Add bandwidth monitoring to Gateway

MERGE REQUEST

Overview

This MR adds bandwidth monitoring to the Gateway. If this approach is approved then I will apply this to the Renter and the Host.

Example for Visual changes (ie Screenshot)

N/A

Issues Closed

#3709

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