[llvm] [LoongArch] Optimize inserting extracted elements (PR #146018)

[via llvm-commits]

tangaac wrote:

Use this patch to support extract i8/i16 type element from hi128 part of 256bit vector.
Please update tests too.
[support-extract-i8-i16-type-element-from-hi128-part.txt](https://github.com/user-attachments/files/21014880/support-extract-i8-i16-type-element-from-hi128-part.txt)


https://github.com/llvm/llvm-project/pull/146018