Add capacity payments revenue option to LPF, AEP, SL financial models

[cpaulgilman]

Capacity Payments are available as a source of revenue for SAM's Merchant Plant and PPA Single Owner model, but not for the partnership flip and sale leaseback models.

For some projects, such as PURPA <20 MW projects in California, projects can earn revenue from both an energy price in $/kWh (with TOD multipliers in California's case) and a capacity payment in $/kW, as described in this Standard Offer Contract (SOC) from Southern California Edison as mandated by the CPUC: https://www.sce.com/procurement/solicitations/purpa-soc.

Although the ITC is scheduled to phase out, based on current law, it will not do so until after 2024 (https://www.seia.org/initiatives/solar-investment-tax-credit-itc), so partnership flip and sale leaseback structures still have a role to play.

Related issue: #205

[brtietz]

This article covers the implications of the IRA on Tax Equity structures: https://segueinfra.com/articles/the-end-of-tax-equity-as-you-know-it

The punchline seems to be that there are still a lot of variables, and tax equity structures might still make sense for large projects. It feels too close to the release to do this, sot adding this issue for Fall 2023 so we can keep discussing and add capacity payments to these financial models. Based on the article, we might also consider adding the tax credit multipliers discussed there, if the transfer market comes to fruition.