* Cleanup Page statusSubject and statusCallback
* Convert Page status from Int to enum
(cherry picked from commit 6ca32710be5bfed851ab695a0d9438c7ab609b24)
# Conflicts:
# app/src/main/java/eu/kanade/tachiyomi/data/download/Downloader.kt
# app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderPageSheet.kt
# app/src/main/java/eu/kanade/tachiyomi/ui/reader/loader/HttpPageLoader.kt
# app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerPageHolder.kt