Allow overloaded functions if one has a single unnamed JSON param

Avoids the breaking change in #1927: If there's a function "my_func" having a single unnamed json param and other overloaded pairs(with any number of params), PostgREST won't be able to resolve a POST request to "my_func".

test/fixtures/schema.sql

@@ -2304,24 +2304,48 @@ $$ language sql;
 
 create or replace function test.unnamed_text_param(text) returns text as $$
   select $1;
-$$ language sql ;
+$$ language sql;
 
 create or replace function test.unnamed_bytea_param(bytea) returns bytea as $$
   select $1::bytea;
-$$ language sql ;
+$$ language sql;
 
 create or replace function test.unnamed_int_param(int) returns int as $$
   select $1;
 $$ language sql;
 
-create or replace function test.overloaded_unnamed_param(json) returns int as $$
+create or replace function test.overloaded_unnamed_param(json) returns json as $$
   select $1;
 $$ language sql;
 
+create or replace function test.overloaded_unnamed_param(bytea) returns bytea as $$
+select $1;
+$$ language sql;
+
+create or replace function test.overloaded_unnamed_param(text) returns text as $$
+select $1;
+$$ language sql;
+
+create or replace function test.overloaded_unnamed_param() returns int as $$
+select 1;
+$$ language sql;
+
 create or replace function test.overloaded_unnamed_param(x int, y int) returns int as $$
   select x + y;
 $$ language sql;
 
+create or replace function test.overloaded_unnamed_json_jsonb_param(json) returns json as $$
+select $1;
+$$ language sql;
+
+create or replace function test.overloaded_unnamed_json_jsonb_param(jsonb) returns jsonb as $$
+select $1;
+$$ language sql;
+
+create or replace function test.overloaded_unnamed_json_jsonb_param(x int, y int) returns int as $$
+select x + y;
+$$ language sql;
+
 create table products(
   id int primary key
 , name text