Add lint for RLS not using initplan for auth.<function>() calls

[olirice]

What kind of change does this PR introduce?

Usage of auth.uid(), auth.role() ... are common in RLS policies.

A naive policy like

    create policy "rls_test_select" on test_table
    to authenticated
    using ( auth.uid() = user_id );

will re-evaluate the auth.uid() function for every row. That can result in 100s of times slower performance https://supabase.com/docs/guides/database/postgres/row-level-security#call-functions-with-select

To resolve that issue, the function calls can be wrapped like "(select auth.uid())" which causes the value to be executed exactly 1 time per query

For example:

    create policy "rls_test_select" on test_table
    to authenticated
    using ( (select auth.uid()) = user_id );

NOTE: This lint requires search_path = '' or 'auth' not in search_path; because qual and with_check are dependent on search_path to determine if function calls include the "auth" schema