[mlir][NFC] Add a new getStridesAndOffset function

The new function is a wrapper around the regular `getStridesAndOffset`
that offers a more compact way (as in writing less code) of getting the
relevant information.

This method is intended to be used only when it is known that the
LogicalResult of the regular `getStridesAndOffset` must be "succeeded".

This warpper will assert on that.

Differential Revision: https://reviews.llvm.org/D139529