Fused GEMM

[jagrit06]

Proposed changes

Fuses gemm, addmm, and block_sparse_mm into one Uber-shader that uses metal function constants for specialization No performance regression has been seen on a M2 Ultra

Checklist

Put an x in the boxes that apply.

• [x] I have read the CONTRIBUTING document
• [x] I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have updated the necessary documentation (if needed)