[llvm] [AArch64] Reland merge index address with large offset into base address (PR #79951)

[via llvm-commits]

vfdff wrote:

> > Only LDRBBroX is supported for the first time.
> 
> I think all the instructions from [f568763](https://github.com/llvm/llvm-project/commit/f5687636415969e6d945659a0b78734abdfb0f06) should be added. Else we miss bugs due to a lack of test coverage.
Done, thanks 

https://github.com/llvm/llvm-project/pull/79951