[mlir][tosa] Cleanups for post-merge review comments in tosa-infer-shapes (#87660)

This change addresses some of the additional review feedback on
https://github.com/llvm/llvm-project/pull/87234

.

A summary of the changes:

1. Cleaned up the language to use 'roll back' rather than revert to
reduce the chance of confusion. Improved some function names as well.
2. Eliminated string comparisons on dialect names.
3. Prevented the introduction of redundant tensor.cast operations for
the same value.

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Co-authored-by: Spenser Bauman <sabauma@fastmail>