feat: add discovery-based Firebolt connections

[kop]

Summary

• Add an opt-in host= discovery connection path for sync and async DB-API connections.
• Pass database, engine, and settings as query parameters for discovery sessions while preserving legacy auth/account/API flows.
• Add unit coverage plus a CI integration test that connects to local Firebolt via discovery.
• Update Core integration CI to install Firebolt from get.firebolt.io, start the local container, and run the core integration suite against it.
• Refactor shared discovery validation/client setup, connection assembly, and test scaffolding to reduce new-code duplication reported by Sonar.

Testing

• pytest tests/unit/db/test_connection.py::test_connect_discovery tests/unit/db/test_connection.py::test_connect_discovery_rejects_legacy_parameters tests/unit/db/test_connection.py::test_connect_discovery_validation tests/unit/async_db/test_connection.py::test_connect_discovery
• pytest tests/unit/db/test_connection.py
• pytest tests/unit/async_db/test_connection.py
• python -m compileall -q src/firebolt/common/discovery.py src/firebolt/db/connection.py src/firebolt/async_db/connection.py tests/unit/discovery_connection_helpers.py
• mypy src/firebolt/common/discovery.py src/firebolt/db/connection.py src/firebolt/async_db/connection.py
• pyflakes src/firebolt/common/discovery.py src/firebolt/db/connection.py src/firebolt/async_db/connection.py tests/unit/discovery_connection_helpers.py tests/unit/db/test_connection.py tests/unit/async_db/test_connection.py
• checked changed source files for lines over flake8's 88-char limit
• pre-commit run black --files ...
• pre-commit run isort --files ...

Note: running both sync and async connection test files in one pytest invocation exposes a pre-existing cross-file cache interaction in test_connect_system_engine_caching; each file passes when run independently. Full pre-commit run --all-files is blocked locally on Python 3.12 by hook environment issues, but the CI Python 3.9 log showed only a fixed E501 line-length failure. Local Docker is unavailable here, so the new end-to-end Firebolt discovery integration test is intended to run in CI.

Linear Issue: FB-1831

  

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
85.1% Coverage on New Code
2.8% Duplication on New Code

See analysis details on SonarQube Cloud