* Inject dependencies from the constructor and use those instead.
* Make getSystemInfo() static since its sole purpose is to collect
global state. This also means it can be safely called from the
Installer without needing to construct this class and its unsafe
dependencies as the Installer was doing previously.
* Remove private 'id' member. This cached the fetchOrInsertId()
return value but was never used.
* Remove selectField() fallback IGNORE-mode insert from fetchOrInsertId().
This existed to handle concurrent writes, but this isn't possible
since all this runs inside a DB_MASTER lock.
* Add missing call to $cache->makeKey().
Avoid passing unformatted strings directly to BagOStuff methods.
Bug: T270540
Change-Id: I984526020ea4d5f0fd6f72b6be527edaf6ab0917
