Update electron statuses for `AWSECSExecutor`

[kessler-frost]

Once separation of workflow and electron statuses is done, the electron level statuses need to be updated to accommodate executor dependent statuses. In this case the following status definitions will be updated:

• REGISTERING - Uploading task and registering the ECS task definition

• PROVISIONING - Corresponds to the ECS task state Provisioning

• PENDING_BACKEND - Corresponds to ECS task states Pending and Activating

• RUNNING - Corresponds to ECS task state Running

• DEPROVISIONING - Corresponds to ECS task states Deactivating, Stopping, and Deprovisioning

• COMPLETING - ECS task is in the Stopped state, result files being retrieved, temporary files being deleted

For the end state, there is a separate class called EndState and contains all possible end state statuses like COMPLETED, FAILED, etc. and thus does not need to be added to the executor dependent status.

Acceptance Criteria:

• Above mentioned statuses need to be updated inside the local executor
• Tests need to be added to verify if those definitions are as expected