Make ordinary FCALL contracts nothrow

[davidwrighton]

Summary

• make FCALL_CHECK and ordinary FCALL_CONTRACT statically and dynamically NOTHROW/GC_NOTRIGGER
• add FCALL_CONTRACT_WITH_FRAME for FCALLs that explicitly establish a frame before exception dispatch
• use the framed contract for IL_Throw, IL_Rethrow, and IL_ThrowExact, including their WASM wrappers
• correct the stale MethodDesc::GetName() contract to NOTHROW; the parameterless overload only returns stored names or converts metadata lookup failures to nullptr

The FCALL audit found only the three IL exception helpers directly enabling GC or dispatching managed exceptions. This draft is intended to validate the stronger dynamic contract across the full CI matrix.

Validation

• build.cmd clr -rc checked
• Checked-runtime smoke covering throw, rethrow, null throw, runtime handles, arrays, strings, GC, threading, marshaling, and math (exit 100)

Broad local testing was intentionally skipped in favor of the CI matrix.

Note

This pull request description was generated with GitHub Copilot.

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