Refactor PatternConstraintImpl
We have two distinct cases for the definition here, where the smaller
does not have metadata, where as the full does have. This saves four
fields in under-documented cases.
Also mark Pattern(Effective)Statement for further refactor so we do
not have to play weird tricks with constraints.
JIRA: YANGTOOLS-1065
Change-Id: I6748ca7fefdb4b2a088324ff9bba821c131fe7ab
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit
49936c5730224b5b5d396499ba56888ce30c3946)