Use MODULE.bazel and avoid directly running npm commands.

[jjh42]

I'm not sure if you directly able to accept this PR if people are relying on the workspace rule but this can at least start a discussion.

This patches flatbuffers for use with bazel modules.
Its based on:
https://github.com/bazelbuild/bazel-central-registry/tree/main/modules/flatbuffers
but removes the npm commands since they conflict with a repo that already uses npm.

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[jkuszmaul]

Getting flatbuffers onto bzlmod would be great; see some prior effort at #8227 and issue reference at #7695. I'd guess no one took the time to review #8227 since I don't see any reason it shouldn't've gotten reviewed.