{v,}ptest can be made more efficient with SVE

[Sonicadvance1]

{v,}ptest is a bit of a weird family of instructions because it sets ZF and CF depending on if the full mask, or negated mask is all zeroes respectively. This is a bit of a faff with ASIMD since it doesn't match semantically, and AVX just adds even more instructions to it.

With SVE they added the new CMP<cc> instructions which set both a predicate register and the NZCV flags. This can reduce the number of instructions that {v,}ptest requires by quite a bit.

Likely worth implementing.