[llvm] [BOLT][NFC] Unify two symbol table iterations (PR #90724)

[Donghee Na via llvm-commits]

corona10 wrote:

@aaupov 
For the CPython build(11083 symbols): 4693µs -> 4194µs (Constantly enhanced) from my environment with handy chrono-based measurement.
But when considering the possibility of noise, I am setting up the clang build.

https://github.com/llvm/llvm-project/pull/90724