rCICF27c11342c4a1: [EventBus] Add dependency seems like a very innocent change, adding in a phan dependency upon CentralNotice. However, we use the same dependency list (recursively) for PHPUnit tests as well, so that change added 64! new dependencies for EventBus, including some very slow ones like Wikibase and Scribunto.
This is much hunch as to what slowed down CI recently, since many of the extensions dependency maps intersect, we're pulling in basically everything. Likely we need to split the phan and phpunit/etc. dependency maps (keeping in mind T193824 as well).