feat(ecs): Enable embedded artifacts for Deploy stage

[atyutyunnik]

This PR will allow for AWS ECS task definition artifacts embedded into the pipelines

[allisaurus]

Thanks for submitting this, @atyutyunnik !
Change LGTM, though I'd like to see info on how this was tested (maybe screenshot of embedded artifact in stage + successful deployment). Also since this is an enhancement to the ECS provider, can you please update the commit msg prefix to "feat(ecs):" so it will show up correctly in future release notes/changelog?

[atyutyunnik]

Sometimes we use a heavily parameterized generic pipeline for multiple environments, instead of having specific pipelines:

Then a task definition available as a JSON from cloudformation output:

Outputs:
...
  UiTaskDef:
    Value:
      Fn::Base64:
        !Sub
          |
          {
              "networkMode": "bridge",
              "family": "compute-test-ui",
              "placementConstraints": [],
              "executionRoleArn": "${InfrastructureStack.Outputs.EcsExecutionRole}",
...

can be transmitted as a parameter to such an initial deployment generic pipeline:

and embed it in Deploy ECS's json:

Of course, when editing such a Deploy ECS's task def artifact editor, it won't show anything (can't render the reference to pipeline's parameter; I think it should rather be grayed out and shown as is, if base64-text can't be decoded)

Yet deployment works just fine:

[allisaurus]

@atyutyunnik appreciate the info on testing! For the prefix change, unfortunately the commit message itself (not just the PR title) needs to be updated to reflect the new prefix. If you can do that and update from master, I think this is good to go.

[atyutyunnik]

sorry for this misunderstanding and late response for I have a number of things going on at the moment. I hope I have done this time as prescribed