[mlir][LLVM] drop `llvm.intr.dbg.value` when promoting in `SROA` or `mem2reg`

[mlir][LLVM] drop `llvm.intr.dbg.value` when promoting in `SROA` or `mem2reg`

This has previously been done for `llvm.intr.dbg.declare`, which is a common occurrence when the debug info points to the variable through the pointer, but may also occur when the `alloca` itself is a local variable in debug info.

Not doing so prevents `SROA` and `mem2reg` from promoting e.g. an `alloca`. We simply drop the value completetly, since there is no meaninful debug info that can be constructed instead as the pointer value is removed.

Differential Revision: https://reviews.llvm.org/D154451