[AArchExpandPseudo] Preserve instruction debug number in expansions

This is an initial attempt at preserving debug information in the pseudo
instruction expansion of the AArch backend. In particular, we preserve
the instruction number required by the InstrRef implementation of live
debug values.

There are many other expansions that need to be considered, but the ones
addressed in this commit should be extremely common, as they handle most
arithmetic and logical instructions.

Differential Revision: https://reviews.llvm.org/D145943