[mlir][linalg] Replace monomorphic contration ops with polymorphic variants.

* Moves `batch_matmul`, `matmul`, `matvec`, `vectmat`, `dot` to the new mechanism.
* This is not just an NFC change, in addition to using a new code generation mechanism, it also activates symbolic casting, allowing mixed precision operands and results.
* These definitions were generated from DSL by the tool: https://github.com/stellaraccident/mlir-linalgpy/blob/main/mlir_linalg/oplib/core.py (will be upstreamed in a subsequent set of changes).

Reviewed By: nicolasvasilache, ThomasRaoux

Differential Revision: https://reviews.llvm.org/D97719