[SVE] Generate overloaded functions for ACLE intrinsics.

The SVE ACLE allows using a short-form for the intrinsics, e.g.
the following two declarations generate the same code:

  svuint32_t svld1(svbool_t, uint32_t const *);
  svuint32_t svld1_u32(svbool_t, uint32_t const *);

using the attribute:
  __clang_arm_builtin_alias

so that any call to svld1(svbool_t, uint32_t const *) will
map to __builtin_sve_svld1_u32.

Reviewers: SjoerdMeijer, miyuki, efriedma, simon_tatham, rengolin

Reviewed By: SjoerdMeijer

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75861