runtime: add statement line caller frames

[cpunion]

Changes:

• Add compact runtime funcinfo and statement-line PC metadata for runtime.Caller, CallersFrames, FuncForPC, Func.FileLine, and stack paths.
• Store DCE-safe string/id records instead of function pointers; keep the post-DCE filtering hook available.
• Compress package/function and root/file strings into shared pools with 16-byte records and uint16 symbol hash buckets.
• Resolve indirect caller paths, function-value entry PCs, closure stub aliases, and first executable statement lines.
• Make lazy table initialization thread-safe and keep func-PC fallback initialization low-allocation.
• Ignore linked-module external declarations when collecting ABI roots.

Local validation:

• macOS: go test ./test/go -run 'TestRuntime(LineInfoAndStack|StatementLineInfo|FuncInfoConcurrentFirstUse)' -count=1
• macOS Go 1.26: llgo test -c github.com/goplus/llgo/test/go, then full compiled test/go binary: PASS
• macOS: go test ./internal/build -run 'TestLinkedModuleGlobals|TestFuncInfoTable|TestPrepareFuncInfo|TestIsFuncInfoEnabled' -count=1
• macOS: go test ./cl -run TestFuncInfoMetadataEmission -count=1; go test ./internal/build/funcinfo -count=1; go test ./ssa -run 'TestClosureFuncDeclValue|TestClosureFuncPtrValue|TestDevLTOGlobalDCEFuncInfo' -count=1
• Linux arm64 container: full performance probes built and ran in an 8 GiB Colima profile; internal funcinfo/build tests, cl, and ssa target tests passed in the low-memory container.

Benchmark methodology:

• Performance cells are best / trimmed avg, using ns or us; trimmed avg drops the min and max run from 11 process runs.
• current is this PR. current+lto is this PR built with full LTO for comparison only; this PR does not change LTO defaults.
• main does not provide valid funcinfo for entry-PC or synthetic-PC FuncForPC/Func.FileLine, so those cells are n/a.
• Size cells are MiB.

Local macOS arm64 performance:

Test	main	go	current	current+lto
entry FuncForPC only	n/a	4/4ns	6/7ns	4/4.2ns
entry Func.Name only	n/a	10/10ns	6/7ns	4/4ns
entry FuncForPC + Func.Name	n/a	13/13.7ns	7/7.1ns	5/5ns
entry Func.FileLine	n/a	9/9.9ns	8/8ns	5/5ns
runtime.Caller(0)	9.3/9.4us	153/156.4ns	44/45.9ns	36/38.3ns
runtime.Caller(1)	5.9/5.9us	171/173.6ns	74/76.4ns	61/62.7ns
runtime.Callers only	13.6/13.7us	123/126.9ns	141/152.9ns	134/140.3ns
CallersFrames.Next first frame	21.3/21.5us	267/270.6ns	351/364.1ns	306/313.2ns
synthetic-PC FuncForPC + Name	n/a	13/13.3ns	43/43.4ns	33/34.4ns
synthetic-PC Func.FileLine	n/a	13/14.4ns	45/46.2ns	35/35.8ns

Local Linux arm64 performance:

Test	main	go	current	current+lto
entry FuncForPC only	n/a	4/4ns	7/7.8ns	5/6.1ns
entry Func.Name only	n/a	10/10ns	6/6.9ns	5/6ns
entry FuncForPC + Func.Name	n/a	13/13.6ns	8/8ns	6/6ns
entry Func.FileLine	n/a	9/10.1ns	8/8.8ns	6/7ns
runtime.Caller(0)	1.3/1.3us	164/168.4ns	50/54.4ns	40/47.8ns
runtime.Caller(1)	4.4/4.5us	178/182.4ns	90/100ns	80/86.7ns
runtime.Callers only	8.4/8.5us	123/127.1ns	160/182.2ns	160/175.6ns
CallersFrames.Next first frame	8.8/8.9us	272/280.4ns	440/446.7ns	380/400ns
synthetic-PC FuncForPC + Name	n/a	15/15ns	52/54.7ns	46/47.1ns
synthetic-PC Func.FileLine	n/a	14/14.9ns	54/57.3ns	48/48.9ns

Local macOS arm64 binary size:

Probe	main	main + DWARF	go	current	current+lto
entry-PC	1.83 MiB	2.42 MiB	2.24 MiB	2.04 MiB	1.59 MiB
caller/stack	1.83 MiB	2.42 MiB	2.26 MiB	2.04 MiB	1.60 MiB

Local Linux arm64 binary size:

Probe	main	main + DWARF	go	current	current+lto
entry-PC	1.78 MiB	4.26 MiB	2.15 MiB	2.07 MiB	1.85 MiB
caller/stack	1.78 MiB	4.27 MiB	2.15 MiB	2.07 MiB	1.86 MiB

Notes:

• Caller source locations, entry-PC function names, and file/line results are correct in the local probes.
• Full LTO improves both size and the remaining lookup costs, but this PR does not change LTO defaults.
• Follow-ups are tracked in Proposal: runtime funcinfo metadata and fast FuncForPC lookup #2004: full-LTO policy, exact entry-PC lookup, and a separate CallersFrames/synthetic-PC fast path.

[codecov]

Codecov Report

❌ Patch coverage is 99.05808% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cl/instr.go	98.71%	3 Missing and 3 partials ⚠️

📢 Thoughts on this report? Let us know!

[cpunion]

Superseded by #2012: the statement-line/funcinfo baseline was reimplemented there as the full Go 1.26 pclntab-style model (statement-level pcline records included), extended by #2016's link-phase table. Review continues on #2012 + #2016.