[mlir] Flip LinAlg dialect to _Both

[mlir] Flip LinAlg dialect to _Both

This one required more changes than ideal due to overlapping generated name
with different return types. Changed getIndexingMaps to getIndexingMapsArray to
move it out of the way/highlight that it returns (more expensively) a
SmallVector and uses the prefixed name for the Attribute.

Differential Revision: https://reviews.llvm.org/D129919