Add download and upload stats to skynet

MERGE REQUEST

Overview

This MR adds download and upload stats for skynet.

Example for Visual Changes

Live test results. 100 download threads, 100 upload threads, 10 threads hitting the stats endpoint

EAvg: 237.1319895ms
Avg:  253.358053ms
min:  1.924350ms
max:  1.740294376s

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