Add portal flag to siac skynet pin

MERGE REQUEST

MR Guidelines

Overview

Add the --portal flag to siac skynet pin so that sia nodes can pin skyfiles that their hosts don't have access to.

Example for Visual Changes

https://asciinema.org/a/FeNabOmTnX44yc1xVwjk021lS

Since the command takes a while here is a screen shot as well.

Checklist

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

• All new methods or updated 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 workflow
• Issue added to Sia-UI repo for new supporting features
• Changelog File Created

Issues Closed