Add opt-in feature flag enable-attributes-dt.kubernetes

[jokuniew]

Description

https://dt-rnd.atlassian.net/browse/DAQ-1441
This PR introduces new Feature Flag feature.dynatrace.com/enable-attributes-dt.kubernetes with default value false

Old properties (dt.kubernetes cluster.id/workload.kind/workload.name) are not added by default to:

• bootstrapper's --attribute args
• OTEL_RESOURCE_ATTRIBUTES (with otlpExporterConfiguration in dynakube)

If feature flag is enabled, old properties are added

How can this be tested?

make go/test (unittest & integration test)

Tested manually by:

make deploy
k create -f dynakube.yaml (with otlpExporterConfiguration, no feature flag set)
k create ns sample-app & k run nginx --image=nginx -n sample-app
k get pod -n sample-app nginx -o yaml |grep dt.kubernetes # no output expected

# add feature flag to dynakube feature.dynatrace.com/enable-attributes-dt.kubernetes: "true"
k delete pod -n sample-app nginx
k run nginx --image=nginx -n sample-app

k get pod -n sample-app nginx -o yaml |grep dt.kubernetes # bootstrapper --attribute & otel's OTEL_RESOURCE_ATTRIBUTES should be listed