Fix incorrect timestamps in CDB_TableMetadata_Text

Instead of performing a proper join on tabname, CDB_TableMetadata_Text joins
cdb_tablemetadata against pg_catalog.pg_class (i.e. All postgres tables,
views, indices, etc.) and gives a record for every possible tabname and
updated_at combination.  This results in the latest updated timestamp being
chosen for any table in CDB_Get_Foreign_Updated_At, which leads to unnecessary
and incorrect cache invalidation.

scripts-available/CDB_TableMetadata.sql

@@ -7,7 +7,7 @@ CREATE TABLE IF NOT EXISTS
 
 CREATE OR REPLACE VIEW public.CDB_TableMetadata_Text AS
        SELECT FORMAT('%I.%I', n.nspname::text, c.relname::text) tabname, updated_at
-       FROM public.CDB_TableMetadata, pg_catalog.pg_class c
+       FROM public.CDB_TableMetadata m JOIN pg_catalog.pg_class c ON m.tabname::oid = c.oid
        LEFT JOIN pg_catalog.pg_namespace n ON c.relnamespace = n.oid;
 
 -- No one can see this