selection handler.

* added partial load mode feature flag and made extract method to handle partial load mode.

when solution is opened in VS, currently we do not know when exactly solution is fully loaded or not. solution explorer might show all files but design time build might not have finished yet so, any semantic operation such as extract method or rename might do wrong thing since it doesn't know that it is dealing with missing information (solution).

we are trying to address this issue with partial load mode, new API platform is working on. basically, we are planning to block most of semantic operations (except completion/quickinfo/goto definition/signature help and navigate to. we might include FAR here as well) during partial load state.

also, for things like squiggle, LB and etc, we will disable those until solution is fully loaded since we don't actually know whether those data is correct or not during partial load state.

this change add featureflag so that we can incrementally add support for each features while dogfooding behavior across partners. as a first attempt, extract method is choosen for new experience.

other internal options are added so that we can try alternative behaviors and etc.

test is not added yet.

* fix merge break

* update string

* small tweak.

* PR feedbacks

* updated the title

* updated after discussing about PR

* do even cheaper version of getting text.

addscope doesn't work with description with blank line when scope is nested. wait dialog seems supporting only 2 lines.

until, I figure out this with platform team, making description one line.

* following PR feedback

* Add Static Symbols classification
* Add Namespace name classification
* Add Label name classification
* Add Overloaded Operator classification
* Add Control Keyword classification
* Updated TaggedText to work with the new classifications
* Add common AbstractNameSyntaxClassifier class for sharing code

Do not crash ExtractMethod when we run into a dataflowanalysis result we didn't account for. (#30554)

* Do not crash when we run into a dataflowanalysis result we didn't account for.

* Add comment.

* remove

* Improve error strings.

* Simplify.

* Assume the variable is read.

* Add test.

* KeyValueMessage.

Added AddMissingImport CodeRefactoring driven by PasteTrackingService

Added PasteTrackingService that handles the paste command and track
paste information for documents. This paste information can be used
by refactorings to make suggestions based on what was pasted.

Fixes #10272

* Add AB tests for code cleanup
revert the text change of Code_cleanup_is_not_configured, as the new text is not translated
Only SettingIsAlreadyUpdatedByExperiment to ture for Group B; always show gold bar if user setting is changed in AB test

* remove usings when format document

* sort usings when format document

* add code fix

* hack fix for the issue with apply multiple changes.

* refactoring

* 3 changes

1. put open file editorconfig change tracking back
2. handle open file leaking when solution close with files opened case
3. don't share locks between editorconfig events and roslyn events

* skip the 'Remove unused variable' when format document

* changed code fix part to use "fix all" and only fixes P1 list rather than fix everything in the document. also not apply changes to buffer until everything is done rather than doing it per fix.

* made undo experience better

* add expression body as one of fix to offer

* add code fix options in format document settings

* add hidden box IsCodeCleanupConfiguredCheckBox to track if the user ever configured the code cleanup

* clean up

* fix some tests

* disable a test temporarily

* PR comments

* refactoring

* Revert "3 changes"

This reverts commit 7e0fd53f02a0e20d063440b3cce5569e51e71afc.

* PR comments

* PR comments

* renaming

* bug fixing

* PR comments

* refactoring

* refactoring

* refactoring

* refactoring

* Make ICodeCleanupService extend ILanguageService

* refactoring

* refactoring

* fix deadlock, call Format inside CodeCleanupService

* rename async methods

* PR comments

* move files under features

* PR comments

* PR comments

* Never Show this again will never show the code cleanup info bar for this user.

* rename

* use ImmutableArray

Fixes
https://devdiv.visualstudio.com/DevDiv/_workitems?id=391624&_a=edit

- Inline Rename fields now consist of a themeable/customizable
background, foreground, and border. The border is used in High Contrast.
- Resolved and Unresolved conflict borders can now be themed &
customized.
- Resolved and Unresolved conflict borders now have different dash
styles so they are distinct from each other and regular Inline Rename
fields. The Dashboard shows a key indicating which type of conflict
corresponds to which border dash style.

Related to #9960

1. Increase opacity
2. Support user configuration of the suggestion tag color.
3. Refresh the color when the user changes fonts and colors.

Fixes #5730

Instead of truncating at 15 characters, we limit the (pixel) width of
the names, allowing WPF to truncate with "..." appropriately.

Fixes #5076

- Introduce instructional text when the dashboard is first shown (or when newName = originalName). This should help users who are used to the pre-VS2015 modal dialog learn to edit the identifier inline in the editor. If we at some point add a way to launch Inline Rename with a new name already specified, we'll need to be a bit more careful about how to both show that new name *and* the instructional text.

- Show the newName as the user types it

- Rearranging the info in the window to flow a bit better:
    - Heading (rename from x to y, or show getting started instructions)
    - Settings
    - Summary (# locations to be updated and any conflict info).

- Slightly changed the reference count text from "found 1 reference in 1 file" (which made sense in large solutions where you saw "Searching..." for a while, which then got replaced with this text) to a more standalone version of "Rename will update 1 reference in 1 file."

Add a new suggested action "FixMultipleSuggestedAction" for IDE layer corresponding to FixMultipleCodeAction and FixMultipleContext. Also implement the FixMultipleOccurrencesService to compute and apply a FixMultipleSuggestedAction.

Subsequent change will use this service to fix (suppress) diagnostics selected in the error list.

Partial fix for internal TFS bug #927616 ""Brace Matching (Highlight)"
Color setting is ignored"

This change adds a new "Brace Matching" color (not to be confused with
the existing "Brace Matching (Highlight)" and "Brace Matching
(Rectangle)" colors) that controls the appearance of brace matching. It
is user customizable and the Background color controls the fill
("Highlight") and the Foreground color controls the outline
("Rectangle").

The default background color was chosen to match Visual Studio 2013's
default "Brace Matching (Highlight)" color.

There will also be a related closed-source change for the themed colors,
and that change will complete the bug.

Fixes internal TFS bug 1098507.

show view preview option. We also now start the rename task during preview and
use its result during apply. Also update unit tests.

changed preview warning tagger name from "Warning" to "Preview Warning" to reduce confusion between compiler warning tag.

Fixes #540 "Stale rename entries in the lightbulb menu"

Prior to this change, dismissed rename tracking sessions continued to
provide codefixes which would silently fail when invoked, without
completing the rename operation.

With this change, we now do the following when rename tracking is
manually dismissed:

- Trigger the diagnostic service to reanalyze the document, thus
removing the rename tracking diagnostic.
- Stop providing a codefix when requested
- Show a dialog if a cached codefix is invoked explaining that the
rename was not performed.

Here are the there user scenarios:

1. The user dismisses rename tracking

    - The lightbulb will continue to show in the margin, regardless of
whether any codefix/refactoring is actually still available.

2. The user expands the lightbulb without it ever having been expanded
before.

    - In this case, we are queried for fixes and will not return any, so
either the lightbulb will disappear or it will contain other relevant
codefixes/refactorings at that position, excluding rename.

3. The user expands the lightbulb after it was previously expanded.

    - Our fix was already cached, so we can only give a reasonable message
when it is invoked.

Once #885 is fixed, we can instead implement IDiagnosticUpdateSource and
avoid forcing diagnostic reanalysis.