[mlir][Linalg] Refactor Linalg creation of loops to allow passing iterArgs - NFC

This revision changes the signatures of helper function that Linalg uses to create loops so that they can also take iterArgs.
iterArgs are asserted empty to ensure no functional change.
This is a mechanical change in preparation of tiling on linalg on tensors to avoid  polluting the implementation with an NFC change.

Differential Revision: https://reviews.llvm.org/D88480