Merge light and dark themes (#5470)

* Merge AMOLED and regular dark themes

This allows all variants of dark themes to use black backgrounds as a
separate preference.

* Merge light and dark themes

* Fix ReaderSeekBar color on Dark Blue theme

* Color fixes

* Fix Dark Blue bars ripple

* Simplify night mode check

(cherry picked from commit 0eadc028b6)

# Conflicts:
#	app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferenceValues.kt
#	app/src/main/java/eu/kanade/tachiyomi/data/preference/PreferencesHelper.kt
#	app/src/main/java/eu/kanade/tachiyomi/ui/base/activity/BaseThemedActivity.kt
#	app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt
#	app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsGeneralController.kt

app/src/main/java/exh/EXHMigrations.kt

@@ -325,12 +325,6 @@ object EXHMigrations {
                         putString(PreferenceKeys.librarySortingMode, newSortingMode.name)
                         putString(PreferenceKeys.librarySortingDirection, newSortingDirection.name)
                     }
-
-                    if (prefs.getString(PreferenceKeys.themeDark, null) == "amoledblue") {
-                        prefs.edit {
-                            putString(PreferenceKeys.themeDark, "amoled")
-                        }
-                    }
                 }
                 if (oldVersion under 21) {
                     // Setup EH updater task after migrating to WorkManager