Added API to result persistence

examples/persistence_example.py

install-checks.sh

setup.cfg

src/iac_scan_runner/api.py

src/iac_scan_runner/cleanup_old_scans.py

src/iac_scan_runner/results_persistence.py

src/iac_scan_runner/results_summary.py

src/iac_scan_runner/scan_runner.py