Add experimental mode config option

OpenTelemetry will be rolled out as an experimental feature of CTA. Due to the complexity of it, there are many things to be refined and they are likely to change in the future. Additionally, OpenTelemetry requires a specific setup on the operations side that can currently (due to the forking in CTA taped) quickly overwhelm a central monitoring DB if misconfigured.

To prevent this, we want an extra safeguard that people have to enable if they want to use this feature. The advantage is that this could be used for more than just OpenTelemetry in the future; any experimental feature can be safeguarded under this.

These options would only hold for the daemon processes (frontend, taped), but could be added to other config files in the future if necessary.

I would propose the following config options. For cta-taped:

taped ExperimentalModeEnabled false

For cta-frontend:

cta.experimental_mode_enabled false

Of course the default value for both of these would be false.