[FEATURE] add processors: set: copy_from

Describe the bug
With Elasticsearch 7.11 (i.e. the version immediately after OpenSearch fork), "copy_from" option for the "set" processor has been introduced, here - https://www.elastic.co/guide/en/elasticsearch/reference/7.11/set-processor.html

this breaks a lot of pipelines, registering pipelines will throw the following error:

Exiting: 1 error: error loading pipeline for fileset system/auth: couldn't load pipeline: couldn't load json. Error: 400 Bad Request: {"error":{"root_cause":[{"type":"parse_exception","reason":"[value] required property is missing","processor_type":"set","property_name":"value"}],"type":"parse_exception","reason":"[value] required property is missing","processor_type":"set","property_name":"value"},"status":400}. Response body: {"error":{"root_cause":[{"type":"parse_exception","reason":"[value] required property is missing","processor_type":"set","property_name":"value"}],"type":"parse_exception","reason":"[value] required property is missing","processor_type":"set","property_name":"value"},"status":400}

a workaround is available and requires to change

processors:
  - set:
      field: myfiled
      copy_from: myvalue

to

processors:
- set:
    field: myfiled
    value: '{{myvalue}}'

Start by locating the set processor implementation and its ingest-pipeline tests, then compare the documented Elasticsearch 7.11 copy_from option with the current configuration handling. Update coverage for a set processor using copy_from and verify that the affected pipelines register without requiring value.