The previous asynchronous approach did not work particularly well,
leading to large janks when switching to custom maps or opening the
mission browser.
This commit introduces two key changes:
* Rule loading for WorldActorInfo and PlayerActorInfo is made
synchronous, in preparation for the next commit which will
significantly optimize this path.
* The full ruleset loading, which is required for map validation,
is moved to the server-side and managed by a new ServerMapStatusCache.
The previous syntax check is expanded to include the ability to run
lint tests.
