SubmitWholeTopic: Use exact topic

Searching by topic is prefix based, which breaks the submitWholeTopic
feature as that relies on on searching by the exact topic.

This patch introduces 2 new fields, EXACT_TOPIC and FUZZY_TOPIC, which
will be used for these two different use cases. For grouping by topic
in the server (to show related changes in the same topic and for submitting
the whole topic) EXACT_TOPIC will be used, while FUZZY_TOPIC will be used
for the user search queries.

Renamed LEGACY_TOPIC to LEGACY_TOPIC2, and the current TOPIC
to LEGACY_TOPIC3, so it matches the numbers in ChangeField.java

Change-Id: Ie44608703aa28e1cf0423ac13dccf8e037d300b4
10 files changed