fix timestep issue with generator fuel cost in subhourly data

[bpulluta]

Update Fuel Cost Calculation to Account for Time Step Duration

Changes

• Modified the fuel cost calculation to correctly account for the time step duration.
• Fuel costs are given per time step (e.g., per 30 minutes), not per hour.
• To get the correct hourly cost, we need to divide the cost per time step by the number of hours in a time step: fuel_cost_per_time_step / hours_per_time_step
• This conversion ensures we're using the correct hourly rate in our calculations.

[bpulluta]

Add a test for the subhourly fuel cost

[Bill-Becker]

Add a test for the subhourly fuel cost

I don't see the test. Can you also see what's going on with the failing Generator tests?

[bpulluta]

Add a test for the subhourly fuel cost

I don't see the test. Can you also see what's going on with the failing Generator tests?

I just put that there as a reminder. @Bill-Becker , i did just add tests for subhourly analysis to the offgrid case

[Bill-Becker]

I think we can close this and this PR replaces it (I also want to avoid those updates to the Project.toml and Manifest.toml - we should not be adding HiGHS.jl to the REopt.jl dependencies.

#453

[bpulluta]

replaced PR with #453