SES-789 - Scroll to bottom of long new message(s) (#1426)

* WIP

* Working - push before cleanup

* Fixes #1316

* Cleanup

* PR review adjustments

* Fixed scrolling when receiving an image based message while keyboard is up

* Prevent auto-scroll to last seen item pos in conversation view if <= 3

* Put back <=3 check to scroll

* Forced scrolling to bottom of long messages (both sent and received) when already at the bottom of the RecyclerView

* Fixes #1364

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Co-authored-by: = <=>
Co-authored-by: AL-Session <160798022+AL-Session@users.noreply.github.com>

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationActivityV2.kt

@@ -2162,7 +2162,10 @@ class ConversationActivityV2 : PassphraseRequiredActionBarActivity(), InputBarDe
         override fun onChanged() {
             super.onChanged()
             if (recyclerView.isScrolledToWithin30dpOfBottom) {
-                recyclerView.scrollToPosition(adapter.itemCount-1)
+                // Note: The adapter itemCount is zero based - so calling this with the itemCount in
+                // a non-zero based manner scrolls us to the bottom of the last message (including
+                // to the bottom of long messages as required by Jira SES-789 / GitHub 1364).
+                recyclerView.scrollToPosition(adapter.itemCount)
             }
         }
     }