Ensure we do not try to inline async versions of pinvokes

[jakobbotsch]

We normally fail inlining of pinvokes when we call getMethodInfo, but if we tried inlining an async variant of a pinvoke then that call would succeed and we would end up breaking in getEHinfo that does not handle this case.

Fix #129782

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[Copilot]

Pull request overview

This PR updates the CoreCLR JIT/EE interface to consistently use the ordinary (non-async-variant) MethodDesc as the source of IL/EH metadata when a method participates in async-variant codegen, preventing the JIT from treating async variants of P/Invokes as inlineable IL methods and later asserting when EH info is requested.

Changes:

• Add MethodDesc::GetOrdinaryVariantIfAsyncVersion() to normalize async-variant methods to their ordinary variant where appropriate.
• Extend CEEInfo::getMethodInfoWorker to take an explicit ilFtn (the method whose IL/header should be used) and update call sites accordingly.
• Update getMethodInfo, a canInline EH-count check path, and CEECodeGenInfo::getEHinfo to use the ordinary variant for IL/EH sourcing.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/vm/method.hpp	Adds a helper to map async-variant methods to their ordinary variant for IL/EH sourcing.
src/coreclr/vm/jitinterface.h	Updates getMethodInfoWorker signature to accept an explicit IL-source MethodDesc.
src/coreclr/vm/jitinterface.cpp	Threads ilFtn through method-info/EH-info paths to avoid inlining/metadata mismatches for async P/Invoke variants.

[jakobbotsch]

The change to use ilFtn in this check is the actual fix for the problem, the rest is just avoiding multiple GetOrdinaryVariant calls.