Fix overloaded computed columns on RPC (#1473)

* fix some typos and spelling

* fix pg_source CTE name should be prefixed with pgrst_

* added tests for overloaded computed columns on patch calls

test/fixtures/privileges.sql

@@ -15,6 +15,7 @@ SET search_path = test, "تست", pg_catalog;
 
 GRANT ALL ON TABLE
     items
+    , items2
     , "articleStars"
     , articles
     , auto_incrementing_pk
@@ -127,8 +128,8 @@ GRANT ALL ON TABLE
     , v1.parents
     , v2.parents
     , v2.another_table
-    , v1.childs
-    , v2.childs
+    , v1.children
+    , v2.children
 TO postgrest_test_anonymous;
 
 GRANT INSERT ON TABLE insertonly TO postgrest_test_anonymous;
@@ -138,8 +139,8 @@ GRANT USAGE ON SEQUENCE
     , items_id_seq
     , callcounter_count
     , leak_id_seq
-    , v1.childs_id_seq
-    , v2.childs_id_seq
+    , v1.children_id_seq
+    , v2.children_id_seq
 TO postgrest_test_anonymous;
 
 -- Privileges for non anonymous users