This op is the batched version of linalg.mmt4d. It performs matrix-matrix-transpose multiplication of batched 4-d (5d) inputs as the following:
```
C[b, m1, n1, m0, n0] = sum_{b, k1, k0}(A[b, m1, k1, m0, k0] * B[b, n1, k1, n0, k0])
```
The current use is to provide `linalg.batch_matmul` a lowering path similar to `linalg.matmul -> linalg.mmt4d`.
Differential Revision: https://reviews.llvm.org/D156912