Modify Final Cashout

[the-Astra]

Allows modify_final_cashout function to be added to card objects in a similar manner to calculate_dollar_bonus, which allows functional behavior based on the final cashout sum (for example, "Round cashout value to nearest factor of X"). While similar to the aforementioned calculate_dollar_bonus, this feature adds capability not previously available without patching

Additional Info:

• I didn't modify api's or I've made a PR to the wiki repo.
• I didn't modify api's or I've updated lsp definitions.
• I didn't make new lovely files or all new lovely files have appropriate priority.