Add optimized ciphertext-plaintext matmul from Tricycle paper

A continuation of https://github.com/google/heir/issues/1376

We added a ct-ct matmul kernel, with modifications from the [Tricycle paper](https://eprint.iacr.org/2025/1200). The same paper has a more optimized kernel for ct-pt matmul (6.1), which should go alongside (or replace?) our existing ct-pt matmul kernel that just "stacks" the Halevi-Shoup kernel.