[llvm] [BOLT][BTI] Disassemble PLT entries when processing BTI binaries (PR #169663)

[Gergely Bálint via llvm-commits]

bgergely0 wrote:

Note: there is [an assert checking that PLT functions' Size must be 0](https://github.com/llvm/llvm-project/blob/main/bolt/include/bolt/Core/BinaryFunction.h#L1310). This never triggered during my local testing. I'm not sure why the `Size` (meaning the original size of the function) was set to 0 though.

https://github.com/llvm/llvm-project/pull/169663