In an effort to make {Ref,Project,Change}Control package-private all
public methods that aren't replaced by PermissionBackend need to move
elsewhere. Both ProjectControl#getLabelTypes() and
ChangeControl#getLabelTypes() rely on the project state, so they
can move there. ChangeControl#getLabelTypes() needs the destination
branch and current user in addition, which are added as arguments.
Change-Id: I080fd93103679552952872dde49cc149a59cd43e
ed5ce1722f