ignore async thunks when iterating the async continuation chain

[max-charlamb]

• Updates CordbAsyncStackWalk::PopulateFrame to ignore methods that are marked IsDiagnosticsHidden(). The relevant case is for async v2 -> async v1 thunks. These don't have debug info and can be skipped in the iteration. Previously this would throw an exception and fail.
• For clarity renames IsILStubOrLCGMethod -> IsDiagnosticsHiddenOrLCGMethod to accurately represent behavior. (Behavior is unchanged in PR.
• Misc whitespace fixes

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[Copilot]

Pull request overview

This PR enhances the async stack walking functionality to skip diagnostic-hidden methods (such as async v2 to async v1 thunks) when iterating the async continuation chain. These thunks lack debug information and should not be exposed as frames in the debugger.

Changes:

• Modified CordbAsyncStackWalk::PopulateFrame to skip DiagnosticsHidden methods during stack iteration
• Renamed IsILStubOrLCGMethod to IsDiagnosticsHiddenOrLCGMethod for naming accuracy
• Renamed enum value kILStub to kDiagnosticHidden to reflect actual behavior
• Applied whitespace cleanup (removed trailing whitespace)

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/coreclr/debug/inc/dacdbiinterface.h	Renamed enum value and interface method, updated comments to reflect DiagnosticHidden terminology
src/coreclr/debug/daccess/dacdbiimpl.h	Updated method declaration to use new name
src/coreclr/debug/daccess/dacdbiimpl.cpp	Implemented method name change, updated return value to kDiagnosticHidden, whitespace cleanup
src/coreclr/debug/di/rsthread.cpp	Updated all call sites to use new method name and enum value, whitespace cleanup
src/coreclr/debug/di/rsstackwalk.cpp	Added loop to skip DiagnosticHidden frames during async stack walk, whitespace cleanup