Remove "Existing" Generator and PV O&M in the developer/owner costs, leave in BAU costs (3rd Party)

[Bill-Becker]

This is not a big deal because not many analyses include a lot of existing Generator and PV and O&M cost is often not a huge cost driver on total lifecycle cost, but:

Update optimization to only apply 3rd-party factor to newly-sized kW for O&M costs. Existing technology O&M costs should have offtaker PWF and tax factors applied to it.

We've updated the calcs in proforma.jl to be this way, but the optimization lumps existing Generator and PV O&M into the developers costs.