[LLVM][InstCombine][AArch64] Refactor common SVE intrinsic combines.

Introduce SVEIntrinsicInfo to store properties common across SVE
intrinsics. This allows a seperation between intrinsic IDs and the
transformations that can be applied to them, which reduces the
layering problems we hit when adding new combines.

This PR is mostly refactoring to bring in the concept and port the
most common combines (e.g. dead code when all false). This will be
followed up with new combines where I plan to reuse much of the
existing instruction simplifcation logic to significantly improve
our ability to constant fold SVE intrinsics.

Author: paulwalker-arm