MM-34758 Collapsed Reply Threads without mobile support (#17424)

Summary
added support for legacy clients accessing server
added collapsed_threads_supported param to viewChannel API and setPostUnread API

Ticket Link
https://mattermost.atlassian.net/browse/MM-34758

Related Webapp PR
mattermost/mattermost-webapp#7933

store/storetest/thread_store.go

@@ -243,7 +243,7 @@ func testThreadStorePopulation(t *testing.T, ss store.Store) {
 		_, err := ss.Thread().UpdateMembership(m)
 		require.NoError(t, err)
 
-		_, err = ss.Channel().UpdateLastViewedAtPost(newPosts[0], newPosts[0].UserId, 0, 0, true)
+		_, err = ss.Channel().UpdateLastViewedAtPost(newPosts[0], newPosts[0].UserId, 0, 0, true, true)
 		require.NoError(t, err)
 
 		assert.Eventually(t, func() bool {
@@ -325,7 +325,7 @@ func testThreadStorePopulation(t *testing.T, ss store.Store) {
 		_, err := ss.Thread().UpdateMembership(m)
 		require.NoError(t, err)
 
-		_, err = ss.Channel().UpdateLastViewedAtPost(newPosts[0], newPosts[0].UserId, 0, 0, true)
+		_, err = ss.Channel().UpdateLastViewedAtPost(newPosts[0], newPosts[0].UserId, 0, 0, true, true)
 		require.NoError(t, err)
 
 		assert.Eventually(t, func() bool {