Optimize simple declared statements
Our declared statements weigh in at 32/56 bytes each, which is
a bit wasteful for what they are doing -- and it all boils down to
class hierarchy.
Introduce AbstractDeclaredStatement, which provides structural
base to implement them with minimal footprint. Initial conversion
includes simple statements, which can be implemented in 16/24 bytes.
OrderedBy statement also takes advantage of low cardinality of its
argument to further eliminate footprint in regular YANG use.
JIRA: YANGTOOLS-1065
Change-Id: I6ea57a7260d3e33108c6c77c1ce120937181796f
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit
ab3c2696f4b6ebc62529570ba39110876c3a3c98)