[AArch64] Add target hook for preferPredicateOverEpilogue

[AArch64] Add target hook for preferPredicateOverEpilogue

This patch adds the AArch64 hook for preferPredicateOverEpilogue,
which currently returns true if SVE is enabled and one of the
following conditions (non-exhaustive) is met:

1. The "sve-tail-folding" option is set to "all", or
2. The "sve-tail-folding" option is set to "all+noreductions"
and the loop does not contain reductions,
3. The "sve-tail-folding" option is set to "all+norecurrences"
and the loop has no first-order recurrences.

Currently the default option is "disabled", but this will be
changed in a later patch.

I've added new tests to show the options behave as expected here:

  Transforms/LoopVectorize/AArch64/sve-tail-folding-option.ll

Differential Revision: https://reviews.llvm.org/D129560