[llvm-branch-commits] [BOLT] Support pre-aggregated returns (PR #143296)

[Amir Ayupov via llvm-branch-commits]

https://github.com/aaupov created https://github.com/llvm/llvm-project/pull/143296

perf can preserve branch type when `save_type` is enabled. This
information is especially valuable for branches from outside the binary
when BOLT can't disassemble the branch source.

This patch adds new pre-aggregated trace type (R).

Test Plan: TBD