refactor speedtest chart

[billimek]

Leverage prometheus and modern speedtest CLI for collecting data. See the following for reference:

• https://github.com/jeanralphaviles/prometheus_speedtest
• https://github.com/topics/speedtest
• https://github.com/topics/speedtest?l=python
• https://pypi.org/project/prometheus-speedtest/
• https://github.com/m-kraus/prometheus-speedtest
• https://github.com/nlamirault/speedtest_exporter
• https://github.com/naa0yama/speedtest_exporter
• https://www.speedtest.net/insights/blog/introducing-speedtest-cli/
• https://github.com/brennentsmith/internet-speed-logger/blob/master/Dockerfile
• https://github.com/pschmitt/docker-ookla-speedtest-cli/blob/master/Dockerfile

[billimek]

Fixed by #214