Implement WFJT prompting for limit & scm_branch

add feature to UI and awxkit

restructure some details of create_unified_job
  for workflows to allow use of char_prompts
  hidden field
avoid conflict with sliced jobs in char_prompts copy logic

update developer docs

update migration reference

bump migration

awxkit/awxkit/api/pages/workflow_job_template_nodes.py

@@ -25,6 +25,7 @@ class WorkflowJobTemplateNode(HasCreate, base.Base):
             'diff_mode',
             'extra_data',
             'limit',
+            'scm_branch',
             'job_tags',
             'job_type',
             'skip_tags',

awxkit/awxkit/api/pages/workflow_job_templates.py

@@ -48,8 +48,9 @@ class WorkflowJobTemplate(HasCopy, HasCreate, HasNotifications, HasSurvey, Unifi
 
         if kwargs.get('inventory'):
             payload.inventory = kwargs.get('inventory').id
-        if kwargs.get('ask_inventory_on_launch'):
-            payload.ask_inventory_on_launch = kwargs.get('ask_inventory_on_launch')
+        for field_name in ('ask_inventory_on_launch', 'limit', 'scm_branch', 'ask_scm_branch_on_launch'):
+            if field_name in kwargs:
+                setattr(payload, field_name, kwargs.get(field_name))
 
         return payload