all: update CI to LLVM payload v8

[zhouguangyuan0718]

Pin GoALLC CI to the published LLVM 23.1.0 v8 payload at revision
445acfc09213ef8f70906a10f32ba96c1d0813c7.

Promote the runtime tests whose backend and GC visibility fixes are included in
the payload/current main:

• abi/method_wrapper.go (LLVM cmd/compile: preserve reflect method reachability in LLVM objects #59)
• fixedbugs/issue78081.go (LLVM cmd/compile: preserve GoObj type identity in LLVM mode #60)
• stackobj2.go (Go cmd/llvmplugin: zero GC-visible allocas after lifetime start #115)

All three pass the local Darwin/arm64 LLVM default<O2> -> GoObj -> link ->
runtime path. PR CI qualifies the released Linux amd64/arm64 artifacts.

The v8 ARM64 layout places the morestack call before the indirect body call.
Update the structured AArch64 frame check to derive exact PCDATA ranges from
call offsets while retaining the strict map association checks: morestack uses
map 0 and the indirect call uses map 1.

devirtualization_nil_panics.go was also evaluated for promotion. Its nil panic
and recover behavior works, but it fails the required source-line assertion
(llvm-ir:1, want line 28). Keep it explicitly gray until the pending Go #117
and LLVM #62 PCLN changes are merged and released; the test itself is not
weakened.

Validation:

• v8 release contains Linux amd64/arm64 archives and SHA256 assets
• JSON/Python parsing and git diff --check
• TestLLVMTestPolicy PASS
• focused LLVM O2 runtime tests for method_wrapper, issue78081, stackobj2 PASS
• full standalone plugin CTest with objview: 64/64 PASS
• devirtualization_nil_panics.go reproduces only the known pcline gap