Add a config to decode json-encoded strings in attribute values

[pxaws]

Description:

This commit adds a config parse_json_encoded_attr_values which is the list of attributes whose values are json-encoded strings. The emf exporter will convert those json-encoded strings as json structures before putting them into the emf log events.

This is to support the aws container insight use case in which json objects are used as field values. For example, like the kubernetes and Sources field in the following emf log event:

{
    "AutoScalingGroupName": "eks-a6bb9db9-267c-401c-db55-df8ef645b06f",
    "ClusterName": "ci-demo",
    "InstanceId": "i-01bf9fb097cbf3205",
    "InstanceType": "t2.xlarge",
    "Namespace": "aws-otel-eks",
    "NodeName": "ip-192-168-12-170.ec2.internal",
    "PodName": "aws-otel-eks-ci",
    "Sources": [
        "cadvisor",
        "calculated"
    ],
    "Type": "PodNet",
    "Version": "0",
    "interface": "eth0",
    "kubernetes": {
        "host": "ip-192-168-12-170.ec2.internal",
        "labels": {
            "controller-revision-hash": "66bb8fc7f4",
            "name": "aws-otel-eks-ci",
            "pod-template-generation": "1"
        },
        "namespace_name": "aws-otel-eks",
        "pod_id": "1810eef4-9121-4e93-8b0a-020c54f7924b",
        "pod_name": "aws-otel-eks-ci-xp66r",
        "pod_owners": [
            {
                "owner_kind": "DaemonSet",
                "owner_name": "aws-otel-eks-ci"
            }
        ]
    },
    "pod_interface_network_rx_bytes": 3166.8867430387045,
    "pod_interface_network_rx_dropped": 0,
    "pod_interface_network_rx_errors": 0,
    "pod_interface_network_rx_packets": 3.7814973119633524,
    "pod_interface_network_total_bytes": 4809.434331265391,
    "pod_interface_network_tx_bytes": 1642.5475882266862,
    "pod_interface_network_tx_dropped": 0,
    "pod_interface_network_tx_errors": 0,
    "pod_interface_network_tx_packets": 2.990021130389628
}

Since the api metric.LabelsMap() in https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/exporter/awsemfexporter/datapoint.go#L106 returns a key value string map, a json object like this

{
        "host": "ip-192-168-12-170.ec2.internal",
        "labels": {
            "controller-revision-hash": "66bb8fc7f4",
            "name": "aws-otel-eks-ci",
            "pod-template-generation": "1"
        },
        "namespace_name": "aws-otel-eks",
        "pod_id": "1810eef4-9121-4e93-8b0a-020c54f7924b",
        "pod_name": "aws-otel-eks-ci-xp66r",
        "pod_owners": [
            {
                "owner_kind": "DaemonSet",
                "owner_name": "aws-otel-eks-ci"
            }
        ]
    }

can't be used directly. To work around the limitation, we stringify the json value and save it as string attribute value in receiver and then restore the original json in emf exporter.

Link to tracking Issue:
#2307

Testing:
Updated the unit tests.

Documentation:
Updated the readme to include the new config.

[codecov]

Codecov Report

Merging #2827 (89c7fca) into main (4df9244) will increase coverage by 1.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2827      +/-   ##
==========================================
+ Coverage   90.51%   91.58%   +1.06%     
==========================================
  Files         449      450       +1     
  Lines       22116    22213      +97     
==========================================
+ Hits        20019    20344     +325     
+ Misses       1632     1397     -235     
- Partials      465      472       +7     

Flag	Coverage Δ
integration	69.09% <ø> (?)
unit	90.52% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
exporter/awsemfexporter/config.go	100.00% <ø> (ø)
exporter/awsemfexporter/emf_exporter.go	100.00% <100.00%> (ø)
exporter/awsemfexporter/factory.go	100.00% <100.00%> (ø)
exporter/awsemfexporter/metric_translator.go	98.17% <100.00%> (+0.25%)	⬆️
internal/common/testing/container/container.go	73.68% <0.00%> (ø)
receiver/jmxreceiver/receiver.go	94.80% <0.00%> (+16.88%)	⬆️
receiver/dockerstatsreceiver/docker.go	92.30% <0.00%> (+39.05%)	⬆️
receiver/dockerstatsreceiver/receiver.go	96.72% <0.00%> (+47.54%)	⬆️
receiver/jmxreceiver/subprocess/subprocess.go	96.55% <0.00%> (+74.48%)	⬆️
receiver/redisreceiver/receiver.go	87.50% <0.00%> (+87.50%)	⬆️
... and 3 more

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