[mlir][vector] Drop trailing 1-dims from constant_mask (#187383)
Generalize TransferReadDropUnitDimsPattern to also drop unit dimensions
when `vector::ConstantMaskOp` is used.
Previously TransferReadDropUnitDimsPattern would only drop unit
dimensions when `vector::CreateMaskOp` with a statically known operand
was used.
Assisted-by: Cursor