JIT: Make multiple try entries in an SCC an implLimitation in fgwasm

[adamperlin]

This case is very rarely hit and would be complicated to fix so it was marked as NYI before. We do hit this in real code, though not in System.Private.CoreLib. Motivated by the following CI failure when compiling Microsoft.Diagnostics.NETCore.Client

Running CrossGen2:  /root/helix/work/correlation/crossgen2/crossgen2 @/root/helix/work/workitem/e/tracing/tracing/Microsoft.Diagnostics.NETCore.Client.wasm.rsp   -r:/root/helix/work/workitem/e/tracing/tracing/IL-CG2/*.dll -f wasm
/__w/1/s/src/coreclr/jit/fgwasm.cpp:351
Assertion failed 'NYI_WASM: SCC with multiple try entry headers' in 'Microsoft.Diagnostics.NETCore.Client.ReversedDiagnosticsServer+<ListenAsync>d__18:MoveNext():this' during 'Wasm transform sccs' (IL size 888; hash 0xeb22f257; FullOpts)

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[Copilot]

Copilot review overview

🟡 Changes recommended

Use IMPL_LIMITATION(...) for diagnostics and correct the comment grammar.

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Review effort: Lite
Findings: 1 · 1

Open (2)

• Use IMPL_LIMITATION to preserve DEBUG diagnostics · New
• Fix subject–verb agreement in comment · New

What changed in this PR

Updates WebAssembly JIT SCC handling to classify multiple try-entry headers as an implementation limitation instead of triggering an NYI assertion.

Changes:

• Replaces the NYI path with implementation-limitation handling.
• Documents the unsupported control-flow case.

File	Description
src/​coreclr/​jit/​fgwasm.cpp	Changes handling of SCCs with multiple try entries.

[Copilot]

Copilot review overview

🔵 Needs a closer look

Add focused regression coverage verifying unsupported methods follow the runtime-JIT-required path instead of asserting.

Review effort: Lite
Findings: 1

Open (1)

• Fix subject–verb agreement in comment

Resolved since last review (1)

• Use IMPL_LIMITATION to preserve DEBUG diagnostics

[Copilot]

Copilot review overview

🔵 Needs a closer look

Add a regression test for the fallback path and correct the diagnostic wording.

Review effort: Lite
Findings: 1

Open (1)

• Fix subject–verb agreement in comment