[flang][hlfir] add matmul canonicalizer

hlfir.matmul_transpose will be lowered to a new runtime call.

A canonicalizer was chosen because
  - Alternative: a new pass for rewriting chained intrinsics - this
    would add a lot of unnecessary boilerplate.
  - Alternative: including this in the HLFIR Intrinsic Lowering pass -
    I wanted to separate these two concerns: not adding a second purpose
    complicating the intrinsic lowering pass.

With this change, the MLIR built-in canonicalization pass should be run
before the HLFIR Intrinsic Lowering pass.

Depends on D145504, D145957

Reviewed By: clementval, vzakhari

Differential Revision: https://reviews.llvm.org/D145959