processor_opentelemetry_envelope: new processor to package non OTel Logs content as OTel

[edsiper]

When collecting data from all plugins except in_opentelemetry, the records comes with basic timestamp, metadata and content; there are cases where this information collected needs to send to be send an OpenTelemetry endpoint (vendor or another OTel compatible endpoint) and packaging with proper OTel Log Resources and Scopes simplify the data transformation.

This processor creates the internal group with OTel basic structure. Note that this creates the envelope, for further processing can be used in conjunction with content modifier processor.

usage example:

pipeline:
  inputs:
    - name: dummy
      samples: 1

      processors:
        logs:
          - name: opentelemetry_envelope

          - name: content_modifier
            context: otel_resource_attributes
            action: upsert
            key: "aaa"
            value: "bbb"

  outputs:
    - name : stdout
      match: '*'

    - name: opentelemetry
      match: '*'
      host: 127.0.0.1
      port: 4318
      logs_uri: /v1/logs

note: there are other small commits in this PR to enable this processor.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.