[llvm] [MCP] Optimize copies when src is used during backward propagation (PR #111130)

[Vladimir Radosavljevic via llvm-commits]

vladimirradosavljevic wrote:

@arsenm @qcolombet I added dedicated MIR test to cover 3 scenarios:
1. Normal case where transformation is performed.
2. Where use is not renamable.
3. Implicit use.

https://github.com/llvm/llvm-project/pull/111130