[CIR] [Lowering] Introduce HoistAllocas Pass

[ChuanqiXu9]

See https://github.com/llvm/clangir/issues/883 for details.

This implements the idea to implement a pass to hoist the allocas and then we can accept the reproducer.

I sent this as a draft since it may be too simple and there are a bunch of test failures due to mismatch. I'll try to fix them if we like this.