Replace "Hide compose button while scrolling" setting with bottom padding (#4486)

As discussed in our contributors meeting.

Advantages:
- last element of list never obscured by action button
- less code that runs on every scroll
- less settings to worry about

Additionally: 
- Added a (smaller) padding to the bottom of lists without action
button, I think it looks nice if there is a bit of white space and the
nav bar divider and the last list divider don't touch.
- The list of filters had no dividers, I added them.
- Recyclerviews with fixed height (Drafts, Filters, edits) now have
scrollbars
- code formatted all touched xml files

closes https://github.com/tuskyapp/Tusky/issues/1563

<img
src="https://github.com/tuskyapp/Tusky/assets/10157047/cd50199f-e84f-4402-93e4-a5a1beba2a08"
width="280"/>

app/src/main/java/com/keylesspalace/tusky/settings/SettingsConstants.kt

@@ -56,7 +56,6 @@ object PrefKeys {
 
     const val SCHEMA_VERSION: String = "schema_version"
     const val APP_THEME = "appTheme"
-    const val FAB_HIDE = "fabHide"
     const val LANGUAGE = "language"
     const val STATUS_TEXT_SIZE = "statusTextSize"
     const val READING_ORDER = "readingOrder"
@@ -112,4 +111,8 @@ object PrefKeys {
 
     /** UI text scaling factor, stored as float, 100 = 100% = no scaling */
     const val UI_TEXT_SCALE_RATIO = "uiTextScaleRatio"
+
+    object Deprecated {
+        const val FAB_HIDE = "fabHide"
+    }
 }