[Matrix] Add minimal lowering pass that only requires TTI.

This patch adds a new variant of the matrix lowering pass that only does
a minimal lowering and only depends on TTI. The main purpose of this pass
is to have a pass with minimal dependencies to run as part of the backend
pipeline.

At the moment, the only difference to the regular lowering pass is that it
does not support remarks. But in subsequent patches add support for tiling
to the lowering pass which will require more analysis, which we do not want
to run in the backend, as the lowering should happen in the middle-end in
practice and running it in the backend is mostly for convenience when
running llc.

Reviewers: anemet, Gerolf, efriedma, hfinkel

Reviewed By: anemet

Differential Revision: https://reviews.llvm.org/D76867