test: add psql-based integration tests for PGOPTIONS handling

[b3b]

What kind of change does this PR introduce?

Tests: adds an integration suite using the psql client to verify PGOPTIONS parsing and propagation.

What is the current behavior?

Existing integration tests only cover protocol-level behavior.
PGOPTIONS handling is currently untested end-to-end, which makes it easy for regressions in startup option parsing to go unnoticed.

What is the new behavior?

This suite launches real psql sessions against Supavisor and verifies the fixes introduced in previous PRs:

• fix: correct PGOPTIONS parsing and search_path handling #768
• fix: apply log_level from options payload during startup #769

CI and configuration changes

• Ensures psql client is installed in GitHub Actions workflow.
• Increases max_pools up to 10 to accommodate new test tenants.
• Tests will skip gracefully if psql is unavailable locally.

Additional context

Tests for known issues that are not yet fixed are marked as skipped:

• Application name is not applied, Prepend application_name from client to application_name set by DbHandler only in session mode #343
• Invalid search_path syntax triggers repeated worker restarts and log flooding - likely not an intended recovery pattern. Maybe a separate issue should be opened for startup error handling?