[mlir][Linalg] Improve codegen strategy

This revision improves the usage of the codegen strategy by adding a few flags that
make it easier to control for the CLI.
Usage of ModuleOp is replaced by FuncOp as this created issues in multi-threaded mode.

A simple benchmarking capability is added for linalg.matmul as well as linalg.matmul_column_major.
This latter op is also added to linalg.

Now obsolete linalg integration tests that also take too long are deleted.

Correctness checks are still missing at this point.

Differential revision: https://reviews.llvm.org/D95531