[BOLT][NFC] Expose YAMLProfileWriter::convert function
The function is to be used by YAML profile emission in BAT mode for
BinaryFunctions not covered by BAT tables (same as in original binary).
Test Plan: NFC
Reviewers: rafaelauler, ayermolo, dcci, maksfb
Reviewed By: dcci
Pull Request: https://github.com/llvm/llvm-project/pull/76909
