[MLIR][Linalg] introduce batch-reduce GEMM

The batch-reduce GEMM kernel essentially multiplies a sequence of input tensor
blocks (which form a batch) and the partial multiplication results are reduced
into a single output tensor block.

See: https://ieeexplore.ieee.org/document/9139809 for more details.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D134163