runtime: fill basic FuncForPC metadata

[cpunion]

Summary

• implement basic runtime.FuncForPC/Func.Name/Func.Entry using native symbol info
• normalize llgo main-package and closure stub symbol names for runtime frames
• add stable test/go coverage for FuncForPC and CallersFrames function metadata
• remove darwin/arm64 xfails for fixedbugs function-metadata cases verified in small batches

Tests

• go test ./test/go -run TestRuntimeFuncMetadataWithLLGo -count=1
• go test ./test/go -count=1
• go test ./test/goroot -count=1 -args -goroot /opt/homebrew/Cellar/go/1.26.0/libexec -dirs fixedbugs -case '^fixedbugs/(issue17381|issue21879|issue29735|issue58300b)\.go$' -directive-mode=ci -run-timeout=2m\n- go test ./test/goroot -count=1 -args -goroot /opt/homebrew/Cellar/go@1.25/1.25.7_1/libexec -dirs fixedbugs -case '^fixedbugs/(issue17381|issue21879|issue29735|issue58300b)\.go$' -directive-mode=ci -run-timeout=2m\n- go test ./test/goroot -count=1 -args -goroot /opt/homebrew/Cellar/go@1.24/1.24.11/libexec -dirs fixedbugs -case '^fixedbugs/(issue17381|issue21879|issue29735|issue58300b)\.go$' -directive-mode=ci -run-timeout=2m\n\n## Notes\n- issue58300.go remains xfailed: reflect.ValueOf(func).Pointer still resolves g to f in the non-pointer-argument case, which appears to be reflect/function-value pointer behavior rather than the symbol-name fix here.\n- line-number/Stack cases remain xfailed because runtime.Caller still lacks PC-to-file:line metadata and runtime.Stack is still a stub.

[cpunion]

Superseded by #1924, which keeps the FuncForPC metadata coverage and adds the function-value wrapper/export fix needed for the failing Linux CI cases.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!