[mlir][tosa] Optimize block scaled cast sequences (#188018)

Add a canonicalization pattern that will delete cast_from_block_scaled
-> cast_to_block_scaled sequences when the input and output types and
block sizes match.

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Signed-off-by: Ian Tayler Lessa <ian.taylerlessa@arm.com>
GitOrigin-RevId: 67d1d984b23f40d6b9e7f97c7e9db40dada0633e