fixes#14961
Adding the license and updating entitlements is flaky, especially at the start of our `coderdent` testing because, while the actual modifications to the `entitlements.Set` were threadsafe, we could have multiple goroutines reading from the database and writing to the set, so we could end up writing stale data.
This enforces serialization on updates, so that if you modify the database and kick off an update, you know the state of the `Set` is at least as fresh as your database update.
* chore: refactor entitlements to be passable as an argument
Previously, all usage of entitlements requires mutex usage on the
api struct directly. This prevents passing the entitlements to
a sub package. It also creates the possibility for misuse.
