Allow telemetry export behaviour to be configured for individual discovery items

[grcevski]

At the moment, which telemetry is exported by OBI is mainly controlled by which export option is chosen. Namely:

1. If OTEL_EXPORTER_OTLP_ENDPOINT is used, we export both metrics and traces for all services which are instrumented.
2. If OTEL_EXPORTER_OTLP_TRACES_ENDPOINT is used, we export traces only.
3. If OTEL_EXPORTER_OTLP_METRICS_ENDPOINT is used, we export metrics only.

It would be beneficial if we had the ability to choose what telemetry is exported and how much for each item in the discovery definition criteria. With this feature, a user can choose to enable higher granularity of telemetry for certain class of services, while keeping the cost of monitoring other less important parts to a minimum.

The proposal is to add an option in the criteria section to specify what we want to generate, including the ability to control some of the telemetry export options, like custom sampling options for traces for a section.