[llvm] [BasicBlockUtils] Remove redundant llvm.dbg instructions after blocks to reduce compile time (PR #89069)

[via llvm-commits]

coderchenlin wrote:

![image](https://github.com/llvm/llvm-project/assets/48561979/c6ac877a-ebe8-4eaf-a3a8-c091f249d941)
the case: https://godbolt.org/z/rrov17cTo
the compile time was reduced a lot,

https://github.com/llvm/llvm-project/pull/89069