Show error when Autometrics functions cannot be loaded

[arendjr]

I intentionally didn't do the same for the metrics loader, because if Prometheus is inaccessible it would likely lead to two errors in that case. It's also unsure if we even keep the metrics overview :)

Resolves #18

[flenter]

Nice, can you add a video showing this in action? I'm curious how clear it is what causes the error/where it comes from.

[arendjr]

Screencast_20230501_173323.webm

Here you go. It's just the standard VS Code functionality though, so I think it's pretty much in line with what users expect anyway :)