Implement getEditableConfigNames for Transitions roles and labels

Problem/Motivation

While working on a site with Config Enforce, we noticed that Workflow Transitions and Labels were not being recognized as "enforceable", even though we were able to identify the relevant config entities through CE's "Generate from Active Storage" feature.

Digging into the problem, I noticed that the getEditableConfigNames() method from ConfigFormBaseTrait has a null implementation in Workflow's WorkflowConfigTransitionFormBase class, from which ConfigTransitionLabelForm and ConfigTransitionRoleForm are derived.

This results in Config Enforce not being able to recognize the config forms and pick up their config entities in context. I'm not aware of other implications, but presumably this missing/null implementation will create similar problems with other modules attempting to interact with Workflow's config entities.

Steps to reproduce

1. Install a site with Config Enforce, Config Enforce Devel, and Workflow modules
2. Create an example workflow entity, eg. my_workflow
3. Go to /admin/config/workflow/workflow/my_workflow/transition_roles, and notice the usual Config Enforce form is missing
4. Go to /admin/config/workflow/workflow/my_workflow/transition_labels, and notice the usual Config Enforce form is missing

Proposed resolution

Implement getEditableConfigNames in both ConfigTransitionLabelForm and ConfigTransitionRoleForm classes, by using the associated Workflow entity's getStates() and getTransitions methods to iterate over Transitions and collect config names for the associated entities.

Remaining tasks

Roll a patch

User interface changes

None, except the Config Enforce form will appear as usual on the associated config forms.

API changes

More complete implementation of the ConfigFormBase API.

Data model changes

None.