Copy rpc (index based)

MERGE REQUEST

Overview

This MR implements the Copy RPC which copies the sector at a certain index and appends it to the end of the host filesystem.

Changes to Work Flow

Copy RPC added

Testing Changes

Existing RPC tests extended

Documentation Changes

RPC README not yet available (followup MR?)

Modules and Packages Impacted

modules, modules/host, modules/renter/proto, siatest/renterhost

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.

• Pipeline Passing (this is for NDFs where tests were run in a loop)
• 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