Fully utilize LinkTarget passed to getRevisionByTitle

Fully utilize LinkTarget passed to getRevisionByTitle

Failure of getRevisionByTitle to pass its LinkTarget argument
to newRevisionFromRow resulted in a needless second instantiation
of the Title (an extra query).

Because newRevisionFromRow needs a Title, not just a LinkTarget,
it is unfortunately necessary to call Title::newFromLinkTarget
on it for now -- however this does not involve a DB lookup and
is on track to be fixed with revisions to the Title class.

Bug: T206498
Change-Id: Ic6f98d8fbf66d85121668571c17e148efc5ec2be