Refactor notifications to Kotlin & paging (#4026)

This refactors the NotificationsFragment and related classes to Kotlin &
paging.
While trying to preserve as much of the original behavior as possible,
this adds the following improvements as well:
- The "show notifications filter" preference was added again
- The "load more" button now has a background ripple effect when clicked
- The "legal" report category of Mastodon 4.2 is now supported in report
notifications
- Unknown notifications now display "unknown notification type" instead
of an empty line

Other code quality improvements:
- All views from xml layouts are now referenced via ViewBindings
- the classes responsible for showing system notifications were moved to
a new package `systemnotifications` while the classes from this
refactoring are in `notifications`
- the id of the local Tusky account is now called `tuskyAccountId` in
all places I could find

closes https://github.com/tuskyapp/Tusky/issues/3429

---------

Co-authored-by: Zongle Wang <wangzongler@gmail.com>

app/src/test/java/com/keylesspalace/tusky/MainActivityTest.kt

@@ -11,8 +11,8 @@ import androidx.work.testing.WorkManagerTestInitHelper
 import at.connyduck.calladapter.networkresult.NetworkResult
 import com.keylesspalace.tusky.appstore.EventHub
 import com.keylesspalace.tusky.components.accountlist.AccountListActivity
-import com.keylesspalace.tusky.components.notifications.NotificationHelper
-import com.keylesspalace.tusky.db.AccountEntity
+import com.keylesspalace.tusky.components.systemnotifications.NotificationHelper
+import com.keylesspalace.tusky.db.entity.AccountEntity
 import com.keylesspalace.tusky.entity.Account
 import com.keylesspalace.tusky.entity.Notification
 import com.keylesspalace.tusky.entity.TimelineAccount