The `isBackendUserLoggedIn()` function of the TSFE array is deprecated
starting with TYPO3 v12 and since the Context API also provides the
necssary aspect and functionality in v11 there is no harm in migrating
now.
Refs: #2
For some reason the AssetCollector instance created (or passed) in the
PageRendererPreProcess constructor was not used, but instead a new
instance was made as part of the addLibrary function.
This commit refactors PageRendererPreProcess::addLibrary to use the
already created AssetCollector.