feat: Enable Batch to optionally marshal data as Events

[lenny-goodell]

Added the IsEventData bool setting so Batch can know to marshal batched data
as []Events before passing to next pipeline function.

In future 3.0 release this flag will be added to the factory methods.

closes #962

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PR Checklist

Please check if your PR fulfills the following requirements:

• I am not introducing a breaking change (if you are, flag in conventional commit message with BREAKING CHANGE: describing the break)
• I am not introducing a new dependency (add notes below if you are)
• I have added unit tests for the new feature or bug fix (if not, why?)
• I have fully tested (add details below) this the new feature or bug fix (if not, why?)
• I have opened a PR for the related docs change (if not, why?)
  feat: Document new IsEventData for Batch function edgex-docs#610

Testing Instructions

1. Run no secure EdgeX stack
2. Clone branch for this PR
3. Clone app-service-configurable and modify go.mod as follows:

replace github.com/edgexfoundry/app-functions-sdk-go/v2 => ../app-functions-sdk-go

4. run make build
5. Modify ./res/functional-tests/configuration.toml as follows:

  ExecutionOrder = "Batch, SetResponseData"

add:
    [Writable.Pipeline.Functions.Batch]
      [Writable.Pipeline.Functions.Batch.Parameters]
      Mode = "bycount" 
      BatchThreshold= "2"
      IsEventData = "true"

6. run ./app-service-configurable -p=functional-tests
7. Using Postman or curl send the the following to localhost:59705/api/v2/trigger

{
    "requestId": "82eb2e26-0f24-48ba-ae4c-de9dac3fb9bc",
    "apiVersion": "v2",
    "event": {
        "apiVersion": "v2",
        "deviceName": "Random-Float-Device",
        "profileName": "Random-Float-Device",
        "sourceName" : "Float32",
        "origin": 1540855006456,
        "id": "94eb2e26-0f24-5555-2222-de9dac3fb228",
        "readings": [
            {
                "apiVersion": "v2",
                "resourceName": "Float32",
                "profileName": "Random-Float-Device",
                "deviceName": "Random-Float-Device",
                "value": "666",
                "origin": 1540855006469,
                "ValueType": "Float32",
                "id": "82eb2e36-0f24-48aa-ae4c-de9dac3fb920"
            }
        ]
    }
}

8. Verify response is 200 w/o any data.
9. Repeat step 7 and validate the response data is as follows:

[
    {
        "apiVersion": "v2",
        "id": "94eb2e26-0f24-5555-2222-de9dac3fb228",
        "deviceName": "Random-Float-Device",
        "profileName": "Random-Float-Device",
        "sourceName": "Float32",
        "origin": 1540855006456,
        "readings": [
            {
                "id": "82eb2e36-0f24-48aa-ae4c-de9dac3fb920",
                "origin": 1540855006469,
                "deviceName": "Random-Float-Device",
                "resourceName": "Float32",
                "profileName": "Random-Float-Device",
                "valueType": "Float32",
                "value": "666"
            }
        ]
    },
    {
        "apiVersion": "v2",
        "id": "94eb2e26-0f24-5555-2222-de9dac3fb228",
        "deviceName": "Random-Float-Device",
        "profileName": "Random-Float-Device",
        "sourceName": "Float32",
        "origin": 1540855006456,
        "readings": [
            {
                "id": "82eb2e36-0f24-48aa-ae4c-de9dac3fb920",
                "origin": 1540855006469,
                "deviceName": "Random-Float-Device",
                "resourceName": "Float32",
                "profileName": "Random-Float-Device",
                "valueType": "Float32",
                "value": "666"
            }
        ]
    }
]

8. Now stop ASC and change config so that IsEventData = "false" and rerun step 7 twice and validate that 2nd response contains the following:

[
    "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",
    "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"
]

New Dependency Instructions (If applicable)

N/A