Add OpenTelemetry to Controllers

[manno]

We want more insight into fleets flow. Spans would allow us to connect events. The existing debug messages lack a common identifier, like a request number.
Hopefully, we could tie spans not only to a request, but also to a resource? So we could see all events e.g. for a git repo.

Notes:

https://opentelemetry.io/docs/instrumentation/go/getting-started/

Problem: wrangler does not pass ctx into the "handler" funcs.

https://pkg.go.dev/context