Fix Boiler Plus SteamTurbine Result

[Bill-Becker]

This pull request adds a new test scenario and makes important corrections to the boiler results calculations to ensure consistent units and accurate annual totals. The main focus is on improving the accuracy of boiler and steam turbine modeling and providing a new test case for validation.

Corrections to Boiler Results Calculations:

• The calculations for annual_fuel_consumption_mmbtu and annual_thermal_production_mmbtu in add_boiler_results now divide by time_steps_per_hour to correctly convert from per-timestep sums to annual totals in MMBtu.
• The thermal_to_steamturbine_series_mmbtu_per_hour output is now correctly converted to MMBtu by dividing by KWH_PER_MMBTU.

New Test Scenario and Validation:

• Added a new scenario file boiler_steamturbine.json that defines a site with boiler and steam turbine parameters for testing.
• Introduced a comprehensive test script test_boiler_steamturbine.jl that runs the scenario, prints key results, and checks the energy balance between boiler output and steam turbine input.