fix for language code capitalization

This is not a user facing string, so must not be localized. Additionally, with https://github.com/dotnet/roslyn/pull/38886, we now support bulk severity configuration in editorconfig based on diagnostic category, so the string ought to be a non-localized constant without any spaces.

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))

Fixes #38050

Improve IDE0060 messages for parameter which has non-zero references, but still can be removed as the initial parameter value is never used.

* Implement lambda discard parameters

* Remove duplicate tests

* Factor logic to recognize underscore tokens

* Align symbol display with other discards

* Distinguish discards in QuickInfo

* Add IsDiscard property instead of IDiscardSymbol

* Adjust IDE logic to use IsDiscard

* Avoid large tuple return

* Add test for ref/out discard parameters

* Address PR feedback and test plan ideas

* Allow in expression trees

* Support general discard parameters

* Add IDE tests

* Emit with unspeakable name

* Remove unused error code

* Only support lambdas

* Fix tests

* Address some PR feedback

* Address remaining feedback

* Address more feedback

* Fix conflict

* Update PublicAPI.Unshipped.txt

* Update PublicAPI.Unshipped.txt

* Add ChangeSignature tests

* Add SymbolCompletion tests

* Add InlineRename test

* 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

This reverts commit fc63c345.

* Report rude edits when updating method containing switch expression.

Fix stackalloc rude edits.

* Updating modifiers of local functions

* await foreach, await using

* Improve error message

* Distinguish async foreach/using from synchronous in error messages

* Using declaration

* Report rude edit when editing using statement/declaration around non-leaf AS

* Rude edits for switch with patterns

* Fix VB issues with active statements in nested single-line functions and when updating iterators

* Update comment

* Fix duplicate rude edit

If it's written to a warning annotation is displayed in the refactoring window to warn that semantics may change.

* Emit tests

* Report rude edits for unsupported DIM operations

* Allow EnC tests to specify TFMs to build against

* EnC: test against netcoreapp30

* Test fixes

* Fix merge

* Top-level types enumeration refactoring

* Simplify DefinitionMap

* Include namespaces in synthesized definition map

* Add SynthesizedNamespaceSymbol

* Embedded Attributes

* Test synthesized attributes

* Clean up EnC tests

* Clean up symbol matcher tests

* Ref readonly return type, in parameter symbol matching tests

* Enable using ref readonly returns, in parameters, ref structs during debugging

* More tests

* ReadOnly struct members

* Fix langauge version mismatch

* Merge fix ups

* Feedback, skip tests