logging: Add basic rate limiting and retention config

This sets up:

• A basic retention config, to delete log data older than two weeks.
• Basic per-stream rate limiting (5 lines/tool/worker/sec, with a burst
  of 100) to prevent a single tool that's spewing out tons of errors
  from consuming all the resources.

It's still missing some higher-up rate limits (ideally there'd be some
sort of per-tool+day limit in Loki itself, but I haven't yet figured out
how to implement that).

Bug: T386480

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Related MRs:

• !807 (merged) (This MR)
• !796 (merged)
• main