processor: inline re-ingestion implementation

[leonardo-albertovich]

This PR adds the concept of processor stages which are just an index that's used to skip the stages that the record has already gone through when re-ingesting them (ie. filter_rewrite_tag) which allows us to resume the process and invoke any remaining processors as expected.

[cosmo0920]

I confirmed that this PR works as expected with my using rewrite_tag configuration:

pipeline:
    inputs:
      - name: dummy
        tag: test-tag.raw
        dummy: '{"tool": "fluent", "sub": {"s1": {"s2": "bit"}}}'
​
        processors:
          logs:
            - name: modify
              match: test-tag.*
              add: hostname monox
            - name: rewrite_tag
              match: test-tag.*
              rule: $tool ^(fluent)$  from.$TAG.new.$tool.$sub['s1']['s2'].out false
              emitter_name: k8s_meta_into_tag_partial_all
            - name: lua
              match: from.test-tag.raw.*
              call: append_tag
              code: |
                function append_tag(tag, timestamp, record)
                  new_record = record
                  new_record["tag"] = tag
                  return 1, timestamp, new_record
                end
​
    outputs:
      - name: stdout
        match: '*'
​
        processors:
          logs:
            - name: lua
              call: add_field
              code: |
                  function add_field(tag, timestamp, record)
                     new_record = record
                     new_record["output"] = "new data"
                     return 1, timestamp, new_record
                  end

I commented a some of nitpicks for naming function which work with processor stage.