[llvm] [FinalizelSel] Re-scan the MachineFunction if we insert a new MBB by custom insertion (PR #96046)

[via llvm-commits]

https://github.com/paperchalice approved this pull request.

LLDB and some LoongArch tests failed, but doesn't look relevant to this pull request.

https://github.com/llvm/llvm-project/pull/96046