Previously we were trying to handle both async and sync use cases in a single function, but it was confusing to read and led to subtle race conditions. This commit separates the async version into a separate function.
- Count deprecations and print them to the console following QUnit runs
- In GitHub actions, write the same information as a job summary
- Add documentation to `discourse-common/lib/deprecated`
- Introduce `id` and `url` options to `deprecated`
- Introduce `withSilencedDeprecations` helper to allow testing deprecated code paths without making noise in the logs
This was previously reverted in 47035693b7.
