refactor / cleanup PointFields code and overall asumptions about numerics

Generalizing this issue to serve as a parent for small individual improvements/cleanup/refactoring subtasks that can be made to various places in the solr code where we deal with Points fields and other older types of numeric fields.

Original description...

As Suggested by Adrien in SOLR-8396

in the below change, it looks like the logic that you apply to point fields would work in the general case and be as efficient?

+    if (ft.isPointField()) {
+      for (String term : terms) {
+        int count = searcher.numDocs(ft.getFieldQuery(null, sf, term), parsed.docs);
+        res.add(term, count);
+      }
+    } else {
+      for (String term : terms) {
+        String internal = ft.toInternal(term);
+        int count = searcher.numDocs(new TermQuery(new Term(field, internal)), parsed.docs);
+        res.add(term, count);
+      }
     }