fix: set pgrst.db_schemas in 0028/0029 tests

[samrose]

Summary

PR #160 added a pgrst.db_schemas filter to lints 0028 and 0029 to scope function findings to schemas PostgREST actually exposes via /rest/v1/rpc. The test SQL files for those lints were not updated to set the GUC, so every positive case in the test stopped firing — the lint correctly returns 0 rows when pgrst.db_schemas is unset, which makes "DEFINER function with EXECUTE to anon" look like a non-finding to the test harness.

This PR sets set local pgrst.db_schemas = 'public'; at the top of both test files, mirroring the established pattern from test/sql/0023_sensitive_columns_exposed.sql (which uses the same filter for the same reason).

Why this slipped past CI

#160's CI run actually reported 2 of 28 tests failed in its log, but the workflow turned green. The cause is in dockerfiles/docker-compose.yml:

command:
  - bash
  - -c
  - "./bin/installcheck; cp /home/splinter/regression.diffs ... 2>/dev/null || true"

bash -c "A; B || true" returns the exit code of the last command — cp ... || true, which is always 0 — so the container exits 0 even when installcheck exits non-zero. The actions run conclusion is therefore success regardless of pg_regress results.

Two tactical options for fixing that, neither in scope for this PR:

1. Replace the ;-and-|| true chain with ./bin/installcheck; rc=$?; cp ... 2>/dev/null || true; exit $rc so the cp still runs (for diagnostics) but the installcheck exit code is preserved.
2. Move the cp into a separate compose service or a post_command hook so the test container can fail cleanly.

Worth a follow-up so future test breakage cannot hide behind a green check.

Verification

SUPABASE_VERSION=15.1.1.13 docker-compose -f dockerfiles/docker-compose.yml run --build --rm test
# All 28 tests passed.

Confirmed locally on supabase/postgres:15.1.1.13. Each positive case in 0028 and 0029 now produces the expected row counts:

• case_definer_default_grant: 1 row (SECURITY DEFINER function created with default PUBLIC EXECUTE).
• case_overloads: 2 rows with distinct cache_key values driven by pg_get_function_identity_arguments.
• All negative cases (INVOKER, EXECUTE-revoked, system-schema) continue to return 0 rows.

Files

• test/sql/0028_anon_security_definer_function_executable.sql — adds set local pgrst.db_schemas = 'public';
• test/sql/0029_authenticated_security_definer_function_executable.sql — same.
• test/expected/0028_anon_security_definer_function_executable.out — re-promoted to include the new echo line.
• test/expected/0029_authenticated_security_definer_function_executable.out — same.