Optimize IdentifiableItemCodec
ImmutableMapTemplate allows us to instantiate space-efficient
ImmutableOffsetMaps very quickly, because we know exactly what
keySet() we are going to use, including our preferred ordering.
Use this class to instantiate keyValueContexts and also create
NodeIdentifierWithPredicates.
JIRA: YANGTOOLS-917
Change-Id: I087083fe4e1914bb5d8e58b9e378ebda9e070793
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit
f6557f4f6831805301ea4690596310fcc03247c3)