Convert exception-related MethodDescCallSite calls to UnmanagedCallersOnly

[AaronRobinsonMSFT]

Summary

Replace MethodDescCallSite/CallDescrWorker calls with more efficient UnmanagedCallersOnly reverse P/Invoke calls in exception handling code paths (priority 2 from #123864).

Changes

Convert the following call sites in excep.cpp to use UnmanagedCallersOnlyCaller:

• GetExceptionMessage: Object.ToString via UCO (METHOD__OBJECT__GET_TO_STRING)
• ExceptionPreserveStackTrace: InternalPreserveStackTrace via UCO
• WrapNonCompliantException: RuntimeWrappedException construction via UCO
• CreateTypeInitializationExceptionObject: TypeInitializationException construction via UCO
• GetResourceStringFromManaged: Environment.GetResourceStringLocal via UCO
• GetEventArgsForNotification: FirstChanceExceptionEventArgs construction via UCO

Pattern

Each conversion follows the established pattern:

1. Add [UnmanagedCallersOnly] static wrapper in managed code with Exception* out-parameter
2. Add corresponding metasig in metasig.h and DEFINE_METHOD in corelib.h
3. Replace MethodDescCallSite + ARG_SLOT with UnmanagedCallersOnlyCaller::InvokeThrowing
4. Remove now-unused DEFINE_METHOD entries for old constructors

All GC references passed to InvokeThrowing are in GCPROTECT'd locations.

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[Copilot]

Pull request overview

This pull request converts six exception-related MethodDescCallSite call sites in excep.cpp to use the more efficient UnmanagedCallersOnly reverse P/Invoke pattern, following the established approach from priority 1 and 2 tasks in issue #123864.

Changes:

• Replaces MethodDescCallSite/CallDescrWorker with UnmanagedCallersOnlyCaller::InvokeThrowing for six exception-handling methods
• Adds six new UnmanagedCallersOnly wrapper methods in managed code (Object.CoreCLR.cs, Exception.CoreCLR.cs, Environment.CoreCLR.cs)
• Updates metasig.h with six new method signatures and corelib.h with updated DEFINE_METHOD entries, removing obsolete constructor definitions

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/coreclr/vm/metasig.h	Adds 6 new metasig definitions for UnmanagedCallersOnly wrappers (PtrObj_PtrStr, PtrObj_PtrObj, PtrStr_PtrStr, PtrException_PtrException, PtrChar_PtrException_PtrObj, PtrException_PtrObj, all with PtrException_RetVoid suffix)
src/coreclr/vm/corelib.h	Updates DEFINE_METHOD entries for the 6 converted methods and removes 3 obsolete constructor entries (TYPE_INIT_EXCEPTION.STR_EX_CTOR, RUNTIME_WRAPPED_EXCEPTION.OBJ_CTOR, FIRSTCHANCE_EVENTARGS.CTOR)
src/coreclr/vm/excep.cpp	Converts 6 call sites to use UnmanagedCallersOnlyCaller: GetExceptionMessage, ExceptionPreserveStackTrace, WrapNonCompliantException, CreateTypeInitializationExceptionObject, GetResourceStringFromManaged, GetEventArgsForNotification
src/coreclr/System.Private.CoreLib/src/System/Object.CoreCLR.cs	Adds GetToString UnmanagedCallersOnly wrapper with Exception* out-parameter
src/coreclr/System.Private.CoreLib/src/System/Exception.CoreCLR.cs	Adds 4 UnmanagedCallersOnly wrappers: InternalPreserveStackTrace, CreateRuntimeWrappedException, CreateTypeInitializationException, CreateFirstChanceExceptionEventArgs
src/coreclr/System.Private.CoreLib/src/System/Environment.CoreCLR.cs	Converts GetResourceStringLocal to UnmanagedCallersOnly pattern with string* in/out parameters