New Features Set + SIP-0044: Staking contract hardening against multiple attack vectors

Main Changes

• Feature: Create V2 struct of LoanReturnData
• Feature: Add setter for rolloverFlexFeePercent in the protocol
• Register missing function signature pauser() in loan token
• Fix SIP-0024 duration
• SIP-0044 - Staking contract Staking contract hardening against multiple attack vectors

Full Changelog:
https://github.com/DistributedCollective/Sovryn-smart-contracts/commits/v1.19.0
v1.18.1...v1.19.0