[AArch64] Remove q and non-q intrinsic definitions from the NEON scalar reduce
pairwise implementation, using an overloaded definition instead.
[AArch64] Refactor the NEON scalar reduce pairwise front-end codegen to remove
unnecessary patterns in tablegen.
[AArch64] Refactor the NEON scalar reduce pairwise intrinsics so that they use
float/double rather than the vector equivalents when appropriate.