[RCP][Staking] Merge PIVX PRs

[CaveSpectre11]

Cherry Pick staking PRs from PIVX

• PIVX-Project/PIVX@09acb52
• [Staking][Wallet] Add Multi-Split functionality to stake output splitting PIVX-Project/PIVX#968
• Revised negative split changes: [Staking][Wallet] Add Multi-Split functionality to stake output splitting PIVX-Project/PIVX#968
• Revised staking algo (when ready) [PoS] Stake Modifier V2 PIVX-Project/PIVX#983