Add a "component_equals" or "predicate" conditional type item model

One of the current problems with the new item model definition is that it requires people making custom items to use the "custom_model_data" component, which some of them don't. A "component_equals" or "predicate" condition would remove this issue, they would be a conditional type (so true/false) like the similar "has_component" (which only checks if the component exists).

Proposed format:

{"property":"component_equals", "component":"", "value":{}}

{"property":"predicate", "predicate":"", "value":{}/""} (same as *["predicate"="value"])

(notice how these two are basically the same, that's because predicates are built for components)