[Enhancement]: Improved DAB CLI appinsights config usage

### What happened?

Improved experience with adding telemetry config via CLI:

1. `add-telemetry` -> indicates you'd be adding new telemetry sections each time. Unclear that you need to use this for "update" as well. What about "delete?

2. `--app-insights-enabled` option can't be used on its own, always needs a connection string. This makes sense if all you're doing is "adding" but doesn't make sense for "update".

### Version

.11rc

### What database are you using?

Azure SQL

### What hosting model are you using?

Local (including CLI)

### Which API approach are you accessing DAB through?

REST

### Relevant log output

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct