CUSTOM SPOOF FORK v3

Combine system.prop (runs at post-fs-data) entries into service.sh so that they're only set if needed
Clean up GMS data pif.prop/pif.json files left over from previous releases to ensure they don't trigger detection
Use custom.pif.json for custom spoofing if it exists, self-contained in the module directory, and restore it after module updates
Move props that need to be changed earlier into post-fs-data.sh
Warn of possible conflict if MagiskHidePropsConfig (MHPC) is installed
Continue to use ShadowHook for now