Document ssh, scp and rsync to balena devices, dev vs prod

[pdcastro]

We have a couple of very good forum posts as starting points, which can be nearly copied and pasted:

• https://forums.balena.io/t/rsync-over-balena-ssh-tunnel/6228/4
• https://forums.balena.io/t/howto-ssh-into-host-device/5312

Closely related docs and CLI issues:

• #1016, #1101, #974
• https://github.com/balena-io/balena-cli/issues/1155
• https://github.com/balena-io/balena-cli/issues/885

[balena-ci]

[pdcastro] This issue has attached support thread https://jel.ly.fish/#/support-thread~bca9f761-840d-46ce-94f8-d66e8b644025

[jellyfish-bot]

[sradevski] This issue has attached support thread https://jel.ly.fish/56a596a6-8ac2-4207-8041-58dcaa74dc0f