Optimize entity eq expressions for missing entity properties

[seadowg]

Currently, a predicate expression like missing_property = 'blah' or missing_property = 'blah' or other_property = 'blah' (where missing_property does not actually exist) will not be optimized by in the same way an expression for property that does exist is. That means that a form that uses an expression like this (possible to account for a later stage in the project) would end up loading the entire entity dataset into memory even though the expression is still value (a child that doesn't exist in XPath always evaluates to '').

This should be improved so that =/!= expressions against missing properties and and/or expressions containing them are still optimized.

[lognaturel]

For expressions without and/or, there was a change going from v2024.3 (unknown properties handled in filter strategy) to v2025.1 (fall through to in-mem). It's likely not a serious performance issue because the case is most likely with empty lists.

@seadowg Can you please link to the code that handled missing properties for expressions without and/or? 🙏