Merge dev15.8.x to dev15.8.x-vs-deps

* make diagnostic analyzer service lazy and not require UI thread.

require ExtensionManager change that got checked into 15.8

* change location where we log number of workspace analyzer references due to it being lazy now.

* PR feedback

Report progress for the actions we're talking while doing code-cleanup.

Fix NRE when handling multiline documentation comments in C#

* Fix discard symbol for declaration pattern

* Remove unnecessary cast

basically this Solution/DocumentBranch strongly holding onto next State causes
old roslyn snapshot to make every snapshot after it to stay in memory.

or worse, it causes a lot of forked solution to be left alive in memory until
certain snapshot goes away.

we will first try to simply get rid of this optimization and see whether we can observe
impact on RPS.

if it somehow shows up, we will change it to weak reference rather than strongly hold onto it

Use default constant value for synthesized local reference for LockTa…

* use correct line ending

* ported https://github.com/mono/monodevelop/pull/5335/files

Fix generating types into an existing file

* Break 'remove unnecessary this/me' into it's own analyzer+codefixer.

* Share code.

* Simplify.

* Simplify code.

* Simplify.

* Add comment.

* Inline method.

* Revert accessibility

* Update tests.

* Move tests.

* Make all edits at once.

* Move files.

* Simplify

make code cleanup run in-proc

add PerformAdditionalCodeCleanupDuringFormattingCheckBox

Merge dev15.8.x to dev15.8.x-vs-deps

Merge dev15.8-preview4-vs-deps to dev15.8.x-vs-deps

Merge dev15.8.x to dev15.8.x-vs-deps

This version includes now required `signers` entry to Willow package manifest.

Merge dev15.8-preview4 to dev15.8-preview4-vs-deps

Merge dev15.8.x to dev15.8.x-vs-deps

Fallback navigate to

Merge dev15.8-preview4 to dev15.8.x

Merge dev15.8-preview4 to dev15.8.x

Skip AttributeTests_WellKnownAttributes.ObsoleteOnVirtual_OnBase on S…

Merge dev15.8-preview4-vs-deps to dev15.8.x-vs-deps

Merge dev15.8.x to dev15.8.x-vs-deps

Skip AttributeTests_WellKnownAttributes.ObsoleteOnVirtual_OnBase on Spanish while investigating failure.

Turn on loc check for dev15.8.x

Merge dev15.8-preview4-vs-deps to dev15.8.x-vs-deps

Merge dev15.7.x-vs-deps to dev15.8-preview4-vs-deps