[BOLT] Improve code sharing between AArch64MCPlusBuilder and core AArch64InstrInfo

The duplication of code to get various properties of the instructions between BOLT's `AArch64MCPlusBuilder` and `AArch64InstrInfo` from LLVM core was mentioned several times throughout discussing the patches for gadget scanner:

* the discussion of #129898
* this thread https://github.com/llvm/llvm-project/pull/134146#discussion_r2054051818 in #134146
* these threads https://github.com/llvm/llvm-project/pull/136147#discussion_r2102787355, https://github.com/llvm/llvm-project/pull/136147#discussion_r2103008272 in #136147

Creating a dedicated issue on this topic.

Compare BOLT's AArch64MCPlusBuilder with LLVM core's AArch64InstrInfo to identify the duplicated instruction-property logic. Read the discussions linked from issues and pull requests #129898, #134146, and #136147 for prior context. Done means the shared responsibility and implementation are agreed and the duplication is reduced.

Written by the indexing model from the issue text.