[Metricbeat] Add ability to collect tags for aws services (#12480)

* Collecting tags from resourcegroupstaggingapi in cloudwatch metricset

* Use aws arn parse function

* Add resource_type_filters as a input parameter

* Change resource_type_filter from a list of strings to string

* Remove getResourceTypeUsingNamespace function and add tags.resource_type_filter

CHANGELOG.next.asciidoc

@@ -236,6 +236,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Add a system/entropy metricset {pull}12450[12450]
 - Allow redis URL format in redis hosts config. {pull}12408[12408]
 - Add tags into ec2 metricset. {issue}[12263]12263 {pull}12372[12372]
+- Collect tags for cloudwatch metricset in aws module. {issue}[12263]12263 {pull}12480[12480]
 
 *Packetbeat*
 

metricbeat/docs/modules/aws.asciidoc

@@ -77,7 +77,7 @@ metricbeat.modules:
 == Metricsets
 
 Currently, we have `ec2`, `sqs`, `s3_request`, `s3_daily_storage` and `cloudwatch` metricset in `aws` module. Collecting `tags`
-for EC2 instances is supported.
+for `ec2` and `cloudwatch` metricset is supported.
 
 * *tags.*: Tag key value pairs from aws resources. A tag is a label that user assigns to an AWS resource.
 
@@ -124,6 +124,8 @@ each S3 bucket.
 === `cloudwatch`
 This metricset gives users the freedom to query metrics from AWS Cloudwatch with
 any given namespaces or specific instance with a given period.
+Please see https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/aws-services-cloudwatch-metrics.html[AWS Services That Publish CloudWatch Metrics]
+for a list of AWS services that publish metrics to CloudWatch.
 
 
 [float]
@@ -179,6 +181,8 @@ metricbeat.modules:
         - name: InstanceId
           value: i-0686946e22cf9494a
     - namespace: AWS/EBS
+    - namespace: AWS/ELB
+      tags.resource_type_filter: elasticloadbalancing
   #regions:
   #  - us-east-1
   #  - us-east-2