Add WaveReadLaneAt tests

[inbelic]

This pr implements testing for the WaveReadLaneAt intrinsic.

• WaveReadLaneAt.[16|32|64].test adds testing of the basic types (and vectors)
• WaveReadLaneAt.udt.test adds testing for a matrix, user defined struct and for floating point edge-case values
• WaveReadLaneAt.index.test adds testing of various use-cases with different indices

Resolves: #144

[spall]

I think a test with divergent control flow would be good. So, something like a switch statement where you call WaveReadLaneAt in one or more of the cases.

[bob80905]

Closing as a dup for now. This also revealed an issue: llvm/llvm-project#153303