docs: Write documentation on collecting traces from user workloads

[andrzej-stencel]

We need high-level documentation for collecting traces from user workloads (applications), similar to https://github.com/SumoLogic/sumologic-kubernetes-collection/blob/v2.11.0/deploy/docs/collecting-kubernetes-events.md for collecting Kubernetes events.

It should describe the frequent use cases, like:

• specifying the pods, namespaces, etc. to collect data from
• customizing the collected data - decorating with metadata, filtering, sampling, etc.

This might (and hopefully should) result in changes to configuration of the collection, so that the common use cases do not force the user to mess with the raw OTC configuration, or even prevent that configuration from being exposed in the values.yaml file.