[RISCV] Add tests for SHFLI and UNSHFLI aliases in Zbp extension

Supplement tests alias of SHFLI and UNSHFLI instructions.

RV32: zip8/zip4/zip2/unzip8/unzip4/unzip2

RV64: zip8.w/zip4.w/zip2.w/zip.w/zip8/zip4/zip2/zip/
      unzip8.w/unzip4.w/unzip2.w/unzip.w/unzip8/unzip4/unzip2/unzip

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D120015