feat: e2e pg_upgrade support for suspend and wake enabled projects

[pcnc]

Contributes to INFRA-2255

• prepare.sh sources common.sh, writes a guard file listing services (adminapi, envoy) that supabase-state should leave alone, and stops supabase-state.service before unmounting /data
• complete.sh guards postgresql before mount, runs setup_state (supabase-state setup --fix-perms --start-services) when the binary exists, and removes the guard at the end of a successful upgrade
• common.sh adds guard_for_state, unguard_for_state, stop_service_if_exists (systemctl cat-based to avoid SIGPIPE under pipefail), and setup_state helpers