Currently, the fetcher uses a trivial strategy to select eviction victims: it picks the first cache file it finds in linear iteration. This means that potentially a file that has just been used gets evicted the next moment. This performance loss can be avoided by even the simplest enhancement of the selection procedure.
Proposed approach: determine an effective yet relatively uncomplex and quick algorithm and implement it in `FetcherProcess::Cache::selectVictims(const Bytes& requiredSpace)`. Suggestion: approximate MRU-retention somehow.
Unit-test what actually happens!