Efficient implementation of Attribute Axis in SQL

Efficient implementation of Attribute Axis in SQL

Attribute Axis is the feature which allows fetching only a single
attribute, e.g. //books[@title='Matilda']/@price -> [15]
This implements the attribute axis feature directly in SQL, giving
much higher performance e.g. for CM-handle ID searches in NCMP.
The native SQL implementation directly returns data leaves from DB,
not requiring conversions to FragmentEntity, DataNode, etc.

Issue-ID: CPS-2623
Signed-off-by: danielhanrahan <daniel.hanrahan@est.tech>
Change-Id: I54f517e47ca6bcddfae356f98857b05fd2e1229e