Refactor `Create` workflow

**What would you like to be added**:
Refactor the `create cluster` workflow to use the Management cluster field which was [added to the command context](https://github.com/aws/eks-anywhere/blob/3f6b8e36934306d4732ba0f9167bcaaa9c65e075/pkg/task/task.go#L35).

**Why is this needed**:
This change will be done to make naming consistent through out the workflows.

Start with the Management cluster field added in pkg/task/task.go at the linked revision, then trace how the create cluster workflow obtains and uses its context. The work is done when that workflow uses the Management cluster field and its naming is consistent with the other workflows.

Written by the indexing model from the issue text.