Fix Conversation page flickers

In this page, 3 conversation lists are implemented by the
ConversationListPreferenceController, these lists updates its contents
in updateState(), which is after the preference screen view created.
So when the first time this page is showed, animations of added contents
will be shown.

The improvement is when the first time, update the list in the
onCreate(), which is called before view creation, instead of the
updateState().

And also do the same thing for RecentConversationsPreferenceController.

Also, to reduce latency,
1. Because currently there are duplicated calls in
NoConversationsPreferenceController to check whether conversations are
exists or not, by removing the duplicated calls and reuse the result
from other controllers, the latency could be reduced.
2. Currently, there are seperated api calls, the
mBackend.getConversations(false) in AllConversationsPreferenceController
and the mBackend.getConversations(true) in
PriorityConversationsPreferenceController, use one
mBackend.getConversations(false) in ConversationListSettings to improve,
this does not change the behavior because the result is filtered in
matchesFilter() both before and after.
3. Currently, we sort conversations first then filter them, change to
filter first then sort to reduce latency.

Fix: 215073227
Test: visual check & robo tests
Change-Id: I028a7fabbbf64cf5627e6615372282a36eb784e5