Provide required callback targets

* Put generated files to disk:
- Add new command line param 'GeneratedFilesOut'
- Route new param through tasks with defaults
- Write out generated files when requested to do so
- Rationalize post generation to avoid uncesseary work
- Add Tests for targets and emit
- Add test to track the fact that we can overwrite files on windows in SxS cases

Ensure that warnaserror works identically for warnings configured in …

Refactor PEMethodSymbol loading of UnmanagedCallersOnly

API review feedback

* Check field type when decoding UnmanagedCallersOnly. New tests for this have been added.
* Small cleanup elements.

* Make UnmanagedCallersOnly decoding consistent with Obsolete
* Remove IsValid tracking. This does mean that there are some otherwise bad UnmanagedCallersOnly attributes that we will no longer interpret as "bad" from metadata, but the effort in tracking this very niche scenario for slightly better errors is not worth the additional complexity.
* More testing.

My simple implementation of GetUnmanagedCallersOnlyAttributeData in PEMethodSymbol would cause all PEMethodSymbols to load all attributes when the data is requested, unnecessarily increasing memory pressure. This refactors the implementation to only load the one attribute we need for it, and to not load the public-facing information that is unneeded for this. In the process, I refactored the method checks to share between regular SourceMethodSymbolWithAttributes and PEMethodSymbols, so the criteria for should be more consistent.

Co-authored-by: NJason Malinowski <jason@jason-m.com>

Throw an exception if we can't parse language version

* Refactoring `GeneratedKind.Generated` to `GeneratedKind.MarkedGenerated`, giving us better future ability to add something like `InferredGenerated` if we want to expose a heuristic.
* Added documentation comments.

Report non-fatal errors for failed tasks

Silently failing is not helpful when your test isn't behaving right.

See #47891

Preserve additional location in non-source files when round tripping …

Do not export IDE0079 (remove unnecessary suppressions) analyzer in C…

Merge VarianceSafetyForStaticMembers into dev16.8

Fixes #46377

Fixes #47942
This is a special IDE-only analyzer that should not be exported in the CodeStyle NuGet package. We still want to retain the code in the shared analyzer layer to allow different analyzer hosts to be able to explicitly instantiate it and enforce it on command line from the CodeStyle package.

Merge remote-tracking branch 'upstream/features/VarianceSafetyForStaticMembers' into VarianceSafetyForStaticMembers_103

Remove PROTOTYPE comments from tests for variance safety with static members.

Ensure IServiceBroker is used on a background thread

* Records: Warn if Equals or GetHashCode is redefined, but not both

* Fix ErrorFacts.Generated.cs

* Apply feedback from @jcouv

* Fix RecordTests.cs due to new warnings - part 1

* Small fix

* Small fixes

* Fix RecordTests.cs due to new warning - part 2

* Fix formatting

* Fix RecodTests.cs due to new warning - part 3

* Fix RecodTests.cs due to new warning - part 4

* Fix RecodTests.cs due to new warning - part 5

* Fix RecodTests.cs due to new warning - part 6

* Fix an unintentional mistake

* Apply feedback

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs

* Apply feedback

* Feedback

* UpdateXlf

* Update DiagnosticTest.cs

* Update RecordTests.cs

* Update WarningLevel to 3

* Fix test: warning level