Since it's introduction, the qrdmlah has been represented as a qrdmulh and a sadd_sat. This doesn't produce the same result for all input values though. This patch fixes that by introducing a qrdmlah (and qrdmlsh) intrinsic specifically for the vqrdmlah and sqrdmlah instructions. The old test cases will now produce a qrdmulh and sqadd, as expected.
Fixes #53120 and #50905 and #51761.
Should this refer to vqadd etc instead?