Add tests for shift by constant, masked shifts and bounded shifts. While here,
sort tests by architecture and keep order of tests consistent (lsh, rshU, rsh).
Change-Id: I512d64196f34df9cb2884e8c0f6adcf9dd88b0fc
Reviewed-on: https://go-review.googlesource.com/c/go/+/351289
Trust: Joel Sing <joel@sing.id.au> Reviewed-by: Michael Munday <mike.munday@lowrisc.org> Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>