[Linalg][Vectorization] Add support for linalg vectorization of a tensor.extract case (#107922)
In https://github.com/llvm/llvm-project/pull/102321 we relaxed the
vectorizer so that when checking for contiguous loads we dont always
have a trailing non unit dim. For example in the test case added we have
`tensor<8x1xf32>` which is now a valid candidate for contiguous load.
However, the logic to check contiguous load assumed that only the
trailing dim will be non unit so this PR just updates that logic to find
the actual non unit dim.