Correct fuel costs in `lifecycle_MG_upgrade_and_fuel_cost` output

[rathod-b]

ExpectedMGFuelCost is for one outage only

[adfarth]

@rathod-b I'm torn on whether this should be how it is now (fuel cost for the worst outage modeled) vs. for all of the outages modeled, or for the worst modeled but assuming it happens every year. In some cases, assuming a very long duration outage happens every year might not actually be realistic. Maybe the best thing to do would be allow a user to choose whether the outage should be assumed to happen once or every year.

FYI this is our tool tip documentation in the web tool results page:
If multiple outages are modeled, this value represents the “worst case” fuel cost across the outages. The fuel costs assume the grid outage occurs in year 1 of the project and does not repeat in subsequent years.

[rathod-b]

In this case I think we can report just Year 1 fuel cost. Since the result key has lifecycle in it, it appears that the output is over 25 years. Maybe the fix is a simple renaming of this result output key or separating MG upgrade from fuel costs.