[llvm] [bolt][aarch64] test to reproduce the issue with ldr reg, literal (PR #165723)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

It would be good to handle this in the suggested pass, also reporting how many times it was applied.
Eliminating any converted islands with no further users sounds like a nice addition on top!

>From discussion, this doesn't appear to be a common case.
If it turns out to be more common than we now think, we could consider keeping the island close to its users, as per assembler's original intent, given it is feasible.

https://github.com/llvm/llvm-project/pull/165723