Reconnect WebSockets when configuration settings change

[EhabY]

Summary

• WebSockets now automatically reconnect when proxy, TLS, or header settings change
• Previously users had to reload the window for these changes to take effect (or trigger a WS reconnect)
• Extracted reusable watchConfigurationChanges utility from remote.ts

Settings that trigger reconnection

• coder.headerCommand
• coder.insecure
• coder.tlsCertFile, coder.tlsKeyFile, coder.tlsCaFile, coder.tlsAltHost
• http.proxy, coder.proxyBypass

Closes #691

[code-asher]

Broadly looks good to me. I do wonder though, if we have a working web socket connection do we really need to reconnect? Could make sense for the proxy settings, if you want to switch to a new proxy or something. For the rest though seems like if we have a working web socket, might as well keep using it.

[code-asher]

Ah but maybe the "reconnect" wording is throwing me off, if the web socket is currently failing to connect, makes sense to force a retry once the settings have changed. But does seem like if the web socket is working we could leave it. Probably not worth the effort though, the settings probably change infrequently.

[EhabY]

But does seem like if the web socket is working we could leave it. Probably not worth the effort though, the settings probably change infrequently.

My thoughts as well, we could in theory just do reconnectIfDisconnected where we check the socket is valid but not sure if it makes sense (also not sure if we can get stuck in a state where the socket is broken without erroring - somehow -)