perf: evaluate row level security optimizations

[dargmuesli]

See this Supabase article on row level security recommendations and evaluate performance optimizations that make sense for us.

Also see:

• https://www.graphile.org/postgraphile/best-practices/#use-language-sql-over-language-plpgsql-where-possible
• https://wiki.postgresql.org/wiki/Inlining_of_SQL_functions