R1:c467cc464fb5

Make most repository reads policy-aware

Summary: Ref T603. This swaps almost all queries against the repository table over to be policy aware.

Test Plan:
- Made an audit comment on a commit.
- Ran `save_lint.php`.
- Looked up a commit with `diffusion.getcommits`.
- Looked up lint messages with `diffusion.getlintmessages`.
- Clicked an external/submodule in Diffusion.
- Viewed main lint and repository lint in Diffusion.
- Completed and validated Owners paths in Owners.
- Executed dry runs…