[cmd/opampsupervisor] Add more context about why the agent exited

[iblancasa]

Component(s)

cmd/opampsupervisor

Is your feature request related to a problem? Please describe.

In the supervisor.go file, there is this comment:

			// TODO: decide why the agent stopped. If it was due to bad config, report it to server.
			// https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/21079

Describe the solution you'd like

Add some information to the logs explaining what went wrong with the agent.

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• cmd/opampsupervisor: @evan-bradley @atoulme @tigrannajaryan

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

Pinging code owners for cmd/opampsupervisor: @evan-bradley @atoulme @tigrannajaryan. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.