[MLIR][Arith] Ensure ConstantOp validates signless integers for vectors (#177857)
Fixes #177818
`arith::ConstantOp::isBuildableWith()` was only checking scalar integers
for signlessness, allowing signed vector element types to pass
validation incorrectly.
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Co-authored-by: Milos Poletanovic <mpoletanovic@syrmia.com>