fix: Make `=` operator with vertices work for hash join

[protodef]

This change adds the following entries to the catalog to make vertex hashable.

• vertex_hash function (and C implementation of it)
• A vertex_ops operator family for hash
• A vertex_ops operator class for vertex type and vertex_ops operator family
• The existing vertex = vertex operator as an access method operator for vertex_ops operator family
• vertex_hash function as a support prodecure for vertex_ops operator family

Run the following SQL statements as a superuser to update the existing catalog.

CREATE FUNCTION pg_catalog.vertex_hash(pg_catalog.vertex)
  RETURNS pg_catalog.int4
  LANGUAGE internal
  IMMUTABLE
  STRICT
  PARALLEL SAFE
  AS 'vertex_hash';

CREATE OPERATOR FAMILY pg_catalog.vertex_ops USING hash;

CREATE OPERATOR CLASS pg_catalog.vertex_ops
  DEFAULT FOR TYPE pg_catalog.vertex
  USING hash
  AS
    OPERATOR 1 pg_catalog.=,
    FUNCTION 1 pg_catalog.vertex_hash(pg_catalog.vertex);