[MachineSink] Clear kill flags of sunk addressing mode registers (#75072)

When doing sink-and-fold, the MachineSink clears the "killed" flags of
the operands of the sunk (and deleted) instruction. However, this is not
always sufficient. In some cases we can create the new load/store
instruction with operands other than the ones present in the deleted
instruction. One such example is folding a zero word extend into a
memory load on AArch64. The zero-extend is represented by a pair of
instructions - `MOV` (i.e. `ORRwrs`) followed by a `SUBREG_TO_REG`. The
`SUBREG_TO_REG` is deleted (it is the sunk instruction), but the new
load instruction mentions operands "killed" in the `MOV`, which is no
longer correct.

To fix this, clear the "killed" flags of the registers participating in
the addressing mode.