[llvm] [AArch64] ConditionOptimizer: replace intra-block scan with map-based algorithm (PR #190455)

[Hussam Alhassan via llvm-commits]

hussam-alhassan wrote:

With further updates this algorithm could be used across block boundaries, meaning both intra- and cross-block cases can be covered by the same improved code. This PR will be followed by further patches to implement those changes.

Any feedback on the comments specifically are highly welcome. I was also debating whether `commitPendingPair` would be better as a lambda function. 

https://github.com/llvm/llvm-project/pull/190455