[TLI][AArch64] Extend SLEEF vectorized functions mapping with VLA functions

This commit extends D134719 "[AArch64] Enable libm vectorized
functions via SLEEF" with the mappings for the scalable functions.

It also introduces all the necessary changes needed to support masked
interfaces.

Reviewed By: danielkiss, sdesmalen

Differential Revision: https://reviews.llvm.org/D146839