[llvm] [BOLT][ICP] Propagate parent hash to newly inserted BBs for BAT (PR #171044)

[Jinjie Huang via llvm-commits]

Jinjie-Huang wrote:

Some background & related PRs:
- Fix incorrect BB index mapping: [PR](https://github.com/llvm/llvm-project/pull/145124/) (WIP)
- Skip mapping zero-hash BBs in BAT as fallback: [PR](https://github.com/llvm/llvm-project/pull/169627) (WIP)

I believe the root cause behind both of these issues is actually the reason mentioned above.

https://github.com/llvm/llvm-project/pull/171044