add pause and resume to siac renter upload

MERGE REQUEST

Overview

This adds 2 new commands. siac renter upload pause [duration] and siac renter upload resume.

Example for Visual Changes (ie Screenshot, asciinema)

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
• Any new packages are added to Makefile and .gitlab-ci.yml
• 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
• Changelog File Created

Issues Closed

Every new API endpoint that is added should have a matching issue created to get the endpoint added to siac. Pass that on to the team please.