Search - previews of classifications should mention ClassificationGrouping

We return a total count, should also show groupings

Triage meeting to decide exact wording

Implementation, could probably move ```ClassificationGroupingColumns.gene_symbol_filter``` (which could be static) somewhere global (ie) ```ClassificationGroupingSearchTerm``` then eg:

```
extras = []
if gs_filter := ClassificationGroupingSearchTerm.gene_symbol_filter(obj):
qs = ClassificationGrouping.filter_for_user(user, ClassificationGrouping.objects.all())
if num_classification_groupings := qs.filter(gs_filter).count():
extras.append(PreviewKeyValue(None, f"ClassificationGroupings: {num_classification_groupings}", dedicated_row=True))
return extras