Improve handling of 12/24 hour timestamps on configuration change.

This fixes an edge case seen on ConversationFragment, where if the
device time format is switched between 12/24 hour format while the app
is running, the old time format will still be displayed when the app
is resumed.

This is due to a design flaw in `DateTimeFormatter.ofLocalizedTime`,
where the time format is statically cached and not updated upon
configuration change. The `LocalTime.formatHours()` extension method
was updated to no longer rely on the misbehaving `ofLocalTime` method.

In addition, `ConversationMessaageComputeWorkers.recomputeFormattedDate`
was designed to skip recomputing non-relative timestamps. This works
in most cases but not this specific edge case. A `force: Boolean` flag
was added to force all items to be updated. And the `force = true` flag
was passed upon `onResume` of the fragment.

Closes #14121

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationFragment.kt

@@ -665,6 +665,11 @@ class ConversationFragment :
     outState.putBoolean(SAVED_STATE_IS_SEARCH_REQUESTED, isSearchRequested)
   }
 
+  override fun onStart() {
+    super.onStart()
+    recomputeMessageDates(forceUpdate = true)
+  }
+
   override fun onResume() {
     super.onResume()
 
@@ -1173,12 +1178,7 @@ class ConversationFragment :
 
     getVoiceNoteMediaController().voiceNotePlaybackState.observe(viewLifecycleOwner, inputPanel.playbackStateObserver)
 
-    val conversationUpdateTick = ConversationUpdateTick {
-      disposables += ConversationMessageComputeWorkers.recomputeFormattedDate(
-        requireContext(),
-        adapter.currentList.filterIsInstance<ConversationMessageElement>()
-      ).observeOn(AndroidSchedulers.mainThread()).subscribeBy { adapter.updateTimestamps() }
-    }
+    val conversationUpdateTick = ConversationUpdateTick { recomputeMessageDates() }
 
     viewLifecycleOwner.lifecycle.addObserver(conversationUpdateTick)
 
@@ -1188,6 +1188,17 @@ class ConversationFragment :
     }
   }
 
+  private fun recomputeMessageDates(forceUpdate: Boolean = false) {
+    disposables += ConversationMessageComputeWorkers
+      .recomputeFormattedDate(
+        context = requireContext(),
+        items = adapter.currentList.filterIsInstance<ConversationMessageElement>(),
+        forceUpdate = forceUpdate
+      )
+      .observeOn(AndroidSchedulers.mainThread())
+      .subscribeBy { adapter.updateTimestamps() }
+  }
+
   private fun initializeInlineSearch() {
     inlineQueryController.onOrientationChange(resources.configuration.orientation == Configuration.ORIENTATION_LANDSCAPE)
 

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/computed/ConversationMessageComputeWorkers.kt

@@ -21,13 +21,14 @@ object ConversationMessageComputeWorkers {
 
   fun recomputeFormattedDate(
     context: Context,
-    items: List<ConversationMessageElement>
+    items: List<ConversationMessageElement>,
+    forceUpdate: Boolean = false
   ): Single<Boolean> {
     return Single.fromCallable {
       var hasUpdatedProperties = false
       for (item in items) {
         val oldDate = item.conversationMessage.computedProperties.formattedDate
-        if (oldDate.isRelative) {
+        if (oldDate.isRelative || forceUpdate) {
           val newDate = ConversationMessage.getFormattedDate(context, item.conversationMessage.messageRecord)
           item.conversationMessage.computedProperties.formattedDate = newDate
           hasUpdatedProperties = true