Support for batched matmul

[DrJessop]

Summary: Matmul was relying on linear infra which didn't support batched second argument. This adds support.

Differential Revision: D84279595

[pytorch-bot]

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❌ 5 New Failures

As of commit e39515a with merge base fca0f38 ():

NEW FAILURES - The following jobs have failed:

• pull / test-qnn-wheel-packages-linux (3.10) / linux-job (gh)
  RuntimeError: Command docker exec -t d2c1d8db5033346fd86c30e331988129eb75b855f6530146a4b7bae2c115456e /exec failed with exit code 1
• pull / test-qnn-wheel-packages-linux (3.11) / linux-job (gh)
  RuntimeError: Command docker exec -t 3d88de5d21ca9cbfe7bbb28caaf9774a885451aeb4d129fb6aa565a373168d34 /exec failed with exit code 1
• pull / test-qnn-wheel-packages-linux (3.12) / linux-job (gh)
  RuntimeError: Command docker exec -t de66b5db01634da4e30f0a10840518ce2ac5c92e14ad8e09c9cebc76d6c3427d /exec failed with exit code 1
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 887c8dc985420d350b94139401d38b5f6555ffb49ee7aa377aca9edb2d124e94 /exec failed with exit code 1
• Test CUDA Builds / test-voxtral-cuda-e2e / linux-job (gh)
  RuntimeError: Command docker exec -t 07d2f33aa2f7632b2b3588276af5ee907c07293655cfd3613ca32ababf316bd1 /exec failed with exit code 2

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[meta-codesync]

@DrJessop has exported this pull request. If you are a Meta employee, you can view the originating Diff in D84279595.

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