EnC: Tweak handling of out-of-sync documents to work around source file content inconsistencies (#40947)

* Do not block in presence of out-of-sync documents.

Instead, ignore any changes made to these documents while debugging until their content matches the source used to build the baseline DLL.

* Only check output PDB, not debugger SymReader, for document checksums.
Turns out SymReader does not support reading document checksums once EnC changes have been applied.

Better handle errors that might occur when validating checksums. Previously some of the errors were not reported as diagnostics.

We previously blocked EnC when we observed a source file that is out-of-sync (i.e. its current content does not match the checksum in the originally built PDB). We can however just ignore these files and report a warning that changes made to this file won’t be applied until the file content is reverted back to the state it was when the PDB was built (the file transitions to “matching” state). Once a file is in matching state it can’t change back to another state. We know that we have not applied any change to the code that was compiled from the file because we ignored the file while it was in out-of-sync state. Therefore we know that any changes made from now on can be safely applied to the debuggee.

If we can’t determine whether a file matches or not due to error reading the PDB or the source file content we can treat it similarly to out-of-sync file. That is, ignore any changes until we are able to confirm the file matches. That can happen if, e.g. the PDB is temporarily locked by another process and unlocked later.

Simplify implementation of GetStatusAsync.

Fixes VSO [1051496](https://dev.azure.com/devdiv/DevDiv/_workitems/edit/1051496) ([VS feedback](https://developercommunity.visualstudio.com/content/problem/880533/edits-were-made-which-cannot-be-compiled-stop-debu.html))

* EnC: Use the current document encoding when reading source text from file.

* Optimization

* EnC: Use the current document encoding when reading source text from file.

* Optimization

* Refactoring

* Refactoring

* Refactoring

* Feedback

* Misc feedback

* Use ValueTask instead of custom task caching

* EnC: Fix document out-of-sync checks when module is not loaded when debugging session starts

Previous change https://github.com/dotnet/roslyn/pull/39295 allowed us to rely on PDB source file checksums when distinguishing between design-time-only documents that should be ignored when applying changes and documents whose changes must be applied to the debuggee. The change did not handle the case when the PDB isn't loaded yet when this check is being performed. This bug resulted in changes not being applied correctly and documents getting out-of-sync in scenarios where the modules were not loaded to the debuggee fast enough.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1013242

* EnC: Compare document content before performing IO while stepping

* Feedback

* EnC: Recover from unexpected exceptions in Emit, ReadChecksum

* Fix typo

* Remove BaseSolution property

* Refactor GetAllAddedSymbolsAsync

* Track documents that do not match the debuggee

* Handle design-time-only documents and documents with no sequence points

* Optimize GetSolutionUpdateStatusAsync for stepping in absence of changes

The PDB reader might be needed later on for mapping local signature of an active method that is first edited in a subsequent generation.

* EnC: fix handing added and design-time-only files

* Fix nullability warnings

* Fix nullable warning

* accesibility -> accessibility

* Acess -> Access

* actua -> actual

* agnotic -> agnostic

* aks -> ask

* Algoritm -> Algorithm

* alphabeitcally -> alphabetically

* Analayzer -> Analyzer

* analyer -> analyzer

* anlysis -> analysis

* Fixes mapping of active statement when changing ctor body from block to expression

* Fix GetAllAddedSymbolsAsync.

- Recover from unexpected exceptions.
- Ignore documents that do not belong to the project being emitted during EnC (these could be e.g. speculative documents created by code fix preview).

Change fields of DocumentAnalysisResults to properties to workaround a bug in the VIL that causes evaluation to fail on them, thus making it hard to see the values while debugging Roslyn.

* Active Statement Handling

* Start active statement tracking on background thread

* Ensure XAPI is initialized before calling Concord APIs.

* Fix up and add comments

* Call UninitializeThread in VisualStudioActiveStatementProvider

* Fixes

* PR feedback

* Use dispose pattern for debugger thread initialization

* Finish test

* PR feedback

* Do not track active statements in projects that do not support Roslyn EnC service (e.g. F#)

* Update comment.

* EnC: Report diagnostics for unexpected recoverable exceptions.

* Tweak NFW reporting

* Account for workspace changes in ActiveStatementTagger

* Unsubscribe event in dispose

* Fix initialization of non-remappable regions for unchanged AS in updated method

* Keep non-remappable regions from previous edit session if no edits were made.

* Update xlfs

* Avoid double-free on cancellation

* Avoid calling DkmWorkList.Cancel for now

* Handle active statement without location

* Move Roslyn to newer toolset packages

1. Move to 1.2.1 compiler toolset package.
2. Move to 1.2.0-beta1 analyzer packages.
3. Turn on IOperation feature flag for all projects as the new analyzer packages have IOperation based analyzers.

* Use the Roslyn wide default CA rulesets for newly added samples project.

* Fix couple of test projects to use the Roslyn wide rulesets for code analysis.

* Move to analyzers 1.2.0-beta2 packages (multiple fixes and enhancements to Roslyn diagnostic analyzers)

* Revert accidental file mode changes.

* Move shipped implicit constructors to public API shipped files.

Fixes #11446