Optimize scenario tests: tests/scenarios/event_backtests/

[MDUYN]

Problem

The event backtest scenario tests in tests/scenarios/event_backtests/ are too slow for CI (they cause Ubuntu runners to timeout). They are currently skipped via @unittest.skip.

Required changes

1. Reduce execution time — The event backtest engine iterates through each time step with multiple DB round-trips per iteration. These tests use long date ranges (100–365 days at 2h intervals = 1200–4380 iterations). Reduce date ranges and/or use coarser time frames to bring each test under ~30 seconds.

2. Use only offline test data from tests/resources/test_data/ — All data sources must reference CSV files located in tests/resources/test_data/ (or its subdirectories). Tests should not depend on data files scattered across tests/resources/data/ or tests/resources/market_data_sources_for_testing/. This ensures tests are self-contained, reproducible, and don't break when external data files are reorganized.

Affected files

• tests/scenarios/event_backtests/test_run_backtest_algorithm_param.py
• tests/scenarios/event_backtests/test_run_backtest_with_pandas_datasources.py
• tests/scenarios/event_backtests/test_run_backtest_single_strategy_param.py (commented out)
• tests/scenarios/event_backtests/test_run_backtest_multiple_strategies_param.py (commented out)
• tests/scenarios/event_backtests/test_run_backtest_strategies_attribute.py (commented out)
• tests/scenarios/event_backtests/test_run_backtests_algorithms_param.py (commented out)

Acceptance criteria

• All tests in this folder run in under 30 seconds each
• All tests use data exclusively from tests/resources/test_data/
• Remove the @unittest.skip decorator once optimized
• Tests pass on both macOS and Ubuntu CI runners