[receiver/hostmetrics] add EntityState entity event as log record for host

[povilasv]

Description:

Add EntityState event for host, implementation is similiar to k8sclusterreceiver. This change sends empty event, which can be used together with resourcedetection processor to add required attributes:

    receivers:
      hostmetrics:
        enabled: true
        metadata_collection_interval: "5m"

    processors:
      resourcedetection/env:
        detectors: ["system", "env"]
        timeout: 2s
        override: false
        system:
          resource_attributes:
            host.id:
              enabled: true
      resourcedetection/region:
        detectors: ["gcp", "ec2", "azure"]
        timeout: 2s
        override: true
      transform/entity-event:
        log_statements:
          - context: log
            statements:
              - set(attributes["otel.entity.attributes"]["otel.entity.id"]["host.id"], resource.attributes["host.id"])
              - set(attributes["otel.entity.attributes"]["host.name"], resource.attributes["host.name"])
              - set(attributes["otel.entity.attributes"]["host.type"], resource.attributes["host.type"])
              - set(attributes["otel.entity.attributes"]["host.image.id"], resource.attributes["host.image.id"])
              - set(attributes["otel.entity.attributes"]["host.image.name"], resource.attributes["host.image.name"])
          - context: resource
            statements:
              - keep_keys(attributes, [""])
    service:
      pipelines:
        logs/entity:
          exporters:
            - otlp
          processors:
            - k8sattributes
            - resourcedetection/env
            - resourcedetection/region
            - transform/entity-event
          receivers:
            - hostmetrics

Link to tracking Issue:

#33927

Testing:

• kind cluster
• unit tests

Documentation:

• added docs

[tigrannajaryan]

In a follow up PR we should add "Interval" as a field to the Entity events and use MetadataCollectionInterval as the value. The "Interval" was proposed after the initial design and is now in the OTEP.

[povilasv]

Agree :)

[povilasv]

FYI: unit test failures seem unrelated:

=== FAIL: . TestConnectorConsume/test_fix_failed_label_not_work (re-run 1) (0.01s)
    logger.go:146: 2024-07-09T19:49:27.049Z	INFO	Started servicegraphconnector
    logger.go:146: 2024-07-09T19:49:27.050Z	INFO	Shutting down servicegraphconnector
    logger.go:146: 2024-07-09T19:49:27.052Z	DEBUG	edge completed	{"client_service": "foo", "server_service": "bar", "connection_type": "", "trace_id": "b3a53e9c2ac533afc48b511c2f368dc1"}
    logger.go:146: 2024-07-09T19:49:27.052Z	DEBUG	edge completed	{"client_service": "foo", "server_service": "bar", "connection_type": "", "trace_id": "c6aafb2dcf4d71c81ae52e50e8f805ee"}
    logger.go:146: 2024-07-09T19:49:27.053Z	DEBUG	edge completed	{"client_service": "foo", "server_service": "bar", "connection_type": "", "trace_id": "7af657de319d6a57967bc241882ea94f"}
    connector_test.go:129: 
        	Error Trace:	/home/runner/work/opentelemetry-collector-contrib/opentelemetry-collector-contrib/connector/servicegraphconnector/connector_test.go:129
        	Error:      	Received unexpected error:
        	            	the following errors occurred:
        	            	 -  resource "map[]": scope "traces_service_graph": metric "traces_service_graph_request_total": missing expected datapoint: map[client:foo connection_type: failed:false server:bar]
        	            	 -  resource "map[]": scope "traces_service_graph": metric "traces_service_graph_request_total": unexpected datapoint: map[client:foo connection_type: failed:true server:bar]
        	            	 -  resource "map[]": scope "traces_service_graph": metric "traces_service_graph_request_total": missing expected datapoint: map[client:foo connection_type: failed:true server:bar]
        	            	 -  resource "map[]": scope "traces_service_graph": metric "traces_service_graph_request_total": unexpected datapoint: map[client:foo connection_type: failed:false server:bar]
        	Test:       	TestConnectorConsume/test_fix_failed_label_not_work

=== FAIL: . TestConnectorConsume (re-run 1) (0.01s)