Allow multiple schemas to be exposed in one instance (#1450)

The schema to use can be selected through the headers `Accept-Profile` for GET/HEAD and `Content-Profile` for POST/PATCH/PUT/DELETE.

This is based on the https://www.w3.org/TR/dx-prof-conneg/ttps://www.w3.org/TR/dx-prof-conneg/ spec.

Also increase all memory tests by 1M(otherwise CI fails).

Co-authored-by: Mahmoud Kassem <MKassem@gk-software.com>
Co-authored-by: Mahmoud Kassem <mahmoud_k@mail.com>

test/fixtures/privileges.sql

@@ -6,6 +6,8 @@ GRANT USAGE ON SCHEMA
     , public
     , "تست"
     , extensions
+    , v1
+    , v2
 TO postgrest_test_anonymous;
 
 -- Schema test objects
@@ -122,6 +124,11 @@ GRANT ALL ON TABLE
     , unit_workdays
     , stuff
     , loc_test
+    , v1.parents
+    , v2.parents
+    , v2.another_table
+    , v1.childs
+    , v2.childs
 TO postgrest_test_anonymous;
 
 GRANT INSERT ON TABLE insertonly TO postgrest_test_anonymous;
@@ -131,6 +138,8 @@ GRANT USAGE ON SEQUENCE
     , items_id_seq
     , callcounter_count
     , leak_id_seq
+    , v1.childs_id_seq
+    , v2.childs_id_seq
 TO postgrest_test_anonymous;
 
 -- Privileges for non anonymous users