* [PictureLoader] Add local override storage and resolution with matcher tests
* [PictureLoader] Address review comments
- Make deleteAllLocalOverrides static; it does not touch instance state
- Drop the now-unused hasCustomArt dead code
- Rename the override install methods to installPrintingOverride /
installPrintingOverrideOnLoad
* [Tests] Give loader matcher tests a writable HOME in CI
Under GitHub's docker runner the process uid has no passwd entry, so HOME
resolves to '/' and the test-mode qttest data dir cannot be created.
SettingsCache's QSettings then drops every write, getPicsPath() comes back
empty, and the loader searches a blank path. Point HOME at a QTemporaryDir
for the duration of the run.
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Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>
