[llvm-branch-commits] [MC][NFC] Use vector for GUIDProbeFunctionMap (PR #102905)

[Amir Ayupov via llvm-branch-commits]

https://github.com/aaupov created https://github.com/llvm/llvm-project/pull/102905

Replace unordered_map with a vector. Pre-parse the section to statically
allocate storage. Use BumpPtrAllocator for FuncName strings, keep
StringRef in FuncDesc.

Reduces peak RSS of pseudo probe parsing from 9.08 GiB to 8.89 GiB as
part of perf2bolt with a large binary.

Test Plan:
```
bin/llvm-lit -sv test/tools/llvm-profgen
```