* chore(ci): upgraded linter to 1.53.3
This flagged a bunch of unused parameters, so the PR is larger than
usual, but 99% mechanical.
* separate lint CI task
* run Lint in separate CI
This removes big shared lock held for for the duration of each request
and replaces it with trivially short lock to capture the current
state of the server/repository before passing it to handlers.
Handlers are now limited to only accessing a small subset of Server
functionality to be able to better reason about them.
