Add PostgreSQL support to pass_or_fail investigator

[KrishnaM256]

Summary

• Add PostgreSQL plugins for loading historical data and storing pass/fail decisions in pass_or_fail.py
• Make psycopg2-binary optional via a [postgresql] extra; document install options in README and sample config
• Harden PostgreSQL decision storage with clearer import errors and graceful connection/insert failure handling

Test plan

• Run pass_or_fail.py with postgresql history/decisions config against a test DB
• Verify core install works without psycopg2 and fails with a clear message when postgresql plugin is selected
• Verify pip install opl-rhcloud-perf-team-core[postgresql] enables the plugins

[jhutar]

Thank you! Linter issues were pre-existing issues.