[llvm] [LV] Add target-independent tests for type-mismatch (PR #130295)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> > , and demonstrate that LoopVectorize only ever interleaves when types mismatch.
> 
> I think I am missing how type mismatch is related to interleaving? Picking the interleave count should be independent of whether access types mismatch I think?

What I'm trying to say is that the examples are not really "vectorized": how would you suggest phrasing this, if there is something to this observation? Otherwise, I can just drop observation, and simply present the tests as-is. 

https://github.com/llvm/llvm-project/pull/130295