feat: add edge label filtering to edge_search and Cypher clause

- Implement edge label filtering in edge_search by accepting a label id argument and filtering edges by label OID during scan.
- Update Cypher clause parser to resolve label names to label ids using the label cache and pass them as gtype integer to edge_search.
- Support label filtering in add_edge_to_query and add_edge_to_query_with_prev_edge.
- Update regression tests to include edge label filter queries.

Author: JoshInnis

postgraph--0.1.0.sql

@@ -6892,7 +6892,7 @@ CREATE OPERATOR @> (
     --JOIN = neqjoinsel
 );
 
-CREATE FUNCTION variable_edge_search(graph_oid gtype, id graphid, min gtype, max gtype)
+CREATE FUNCTION variable_edge_search(graph_oid gtype, id graphid, min gtype, max gtype, label_filter text[] DEFAULT NULL)
 RETURNS TABLE  (edges variable_edge, endid graphid, hset hashset)
 CALLED ON NULL INPUT
 STABLE