[llvm] [DSE] Introduce `eliminateRedundantStoresViaDominatingConditions` (PR #181709)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

Current compile-time: [c-t](https://llvm-compile-time-tracker.com/compare.php?from=817b7f33332e7f03b47fc3d1d6f94e5527635748&to=4596d50d3922cd239beb0c5b588dae38c5a9edd2&stat=instructions:u.).

Compile-time using ScopedHashTable: [c-t](https://llvm-compile-time-tracker.com/compare.php?from=da8d1b52d0d344068a8bd3e46a8af3a692d2efc2&to=3f629603ce2e1b6899d07c388fb03099927e5945&stat=instructions:u).

Previous concerns on compile-time turned out to be unfounded. Updated, thanks (admittedly, with the RAII scoping looks much more elegant).

https://github.com/llvm/llvm-project/pull/181709