Use Query Cache for separate loading queries during entity fetching

[dtaimanov]

• Platform version: 7.2.X

See forum topic to find reproducible case.

Problem

Separate loading of collection attribute (org.eclipse.persistence.internal.indirection.QueryBasedValueHolder#instantiate(...):147) does not use Query Cache.
When entity loaded with cached query, and further loading occurs during fetching according to view, nested entities loaded by not cached queries. It leads to repetitive loadings of entity graphs for each cached query if they are not subsequent.

Proposition

Investigate the possibility of "cached" property propagation for "nested" (fetching) queries in value holders.
Or rework fetching mechanism for cached queries to perform "nested" queries manually with "cached" flag, but not through QueryBasedValueHolder