Factory that resolves the slot-template registry for <cngx-filter-builder>.
For each of the nine slots it runs the three-stage cascade and returns the
resolved TemplateRef set the recursive body renders:
the consumer's contentChild slot template
else CNGX_FILTER_BUILDER_CONFIG.templates.<key>
else the built-in default
Default: createFilterBuilderTemplateRegistry. Swap the whole resolution
strategy by providing your own factory at root or component scope: