To facilitate sharing LoopIdiomTransform between AArch64 and RISC-V,
this first patch moves AArch64LoopIdiomTransform from lib/Target/AArch64
to lib/Transforms/Vectorize and renames it to LoopIdiomVectorize. The
following patch (#94082) will teach LoopIdiomVectorize how to generate VP
intrinsics (in addition to the current masked vector style) in favor of
RVV.
