[AArch64][SVE] Add bfloat16 to outstanding tuple vector intrinsics

Summary:
* svget2/3/4
* svset2/3/4
* svcreate2/3/4
* svundef/2/3/4

Reviewers: sdesmalen, kmclaughlin, fpetrogalli, efriedma

Reviewed By: fpetrogalli

Differential Revision: https://reviews.llvm.org/D82665