Closes#14244.

Adds a docs page on the most common reasons why a user might not be able to establish a direct connection to their workspace, or why the connection quality might be degraded, and how they might go about resolving these issues. Replaces the old troubleshooting section on the networking index.

Additionally,coder ping links to this documentation if a direct connection could not established, or if there were any diagnostics printed, or if the verbose flag is set.

Will add the page to the docs restructure branch once this is merged. Done