[processor/k8sattributes] Operator resource attributes

[zeitlinger]

Description

The OTel operator has a set of rules to create resource attributes - which is described here.

This PR allows the collector to create resource attributes with the same logic.

Why

If the operator supplies resource attributes (that are sent with OTLP), it seems redundant that the collector should be able to do the same - it will just overwrite the resource attribute with identical values.

This feature gets interesting if you are not only getting all data from OTLP - but some data elsewhere, e.g. from the file log receiver.

It's crucial to use the same values for resource attributes across signals - this makes correlation possible.
For example, it allows you to find file based the log entries on the same service instance as a trace you're viewing (around the same time).

Alternatives

The same result can be achieved using the transforprocessor - but it's a very long and hard-to-understand configuration.
It that way, it's similar to the container parser.

Testing

Unit tests were added - e2e tests later

Documentation

Added here
This also has a complete config.

[fatsheep9146]

Could you please add a changelog and also updating the document to describe how to use this feature?

[zeitlinger]

@fatsheep9146 added changelog and docs

I also tried adding e2e tests - but didn't get it to work. Please advise if/how to do this.