Support Drools automatic fact eviction

Since this Drools commit, many OP tests broke.

This is because OP relies on Drools to keep references even to the facts that are now automatically evicted. There are several ways of addressing the issue:

• Disabling immutable KIE session; this is a performance improvement we do not want to give up.
• Introduce OP side cache for all inserted facts; this would have a not insignificant impact on OP performance.
• Ask Drools to make a switch to disable this eviction behavior; this is suboptimal, as the cache is still kept somewhere. Only this time, it is in Drools.
• Remove the fail-fast on OP side and re-insert if there is nothing to update. This is the least of all evils and will be the approach chosen.

This is a blocker for the 8.30.0.Final release.