RenewAndClearContract - RPC

MERGE REQUEST

Overview

This MR adds a new Renew RPC which also cleans the contract old contract when renewing it. This has the following advantages.

1. The host doesn't need to increment the reference counter for sectors which is very expensive to do for large contracts
2. The host doesn't need to provide a storage proof for the old contract. This reduces the space on the blockchain required when submitting the final revision.

Example for Visual changes (ie Screenshot)

N/A

Issues Closed

N/A

Checklist

Review and complete the checklist to ensure that the MR is complete before assigned to an approver.

• All new methods, or updating methods have clear docstrings
• Testing added or updated for new methods
• API documentation updated for API updates
• Module README.md updated for changes to work flow
• Issue added to Sia-UI repo for new supporting features