Dynamically provide action plugins for every moderation state change

Updated #65

Problem/Motivation

• Install content_moderation
• Apply the "Editorial" workflow to articles.
• Create an article node in the published workflow state.
• Goto /admin/content
• Use the bulk action "Unpublish content" on the article node.
• You will see this validation error:
  

Proposed resolution

• Remove the publish/unpublish action
• Provide action plugins for every state
• Dynamically create/update/delete action instances when workflow settings are changed.
• Update moderation_content admin view with the state actions.

Remaining tasks

Dynamically create/update/delete action instances when:

• create/update/delete operation happens on a workflow entity by implementing hook workflow (insert|update|delete).
• changes to the workflow entity happen during config import.
• changes to the workflow entity are done hook_update_N.

Update moderation_content admin view with the state actions.
Add functional test for both cases.

User interface changes

moderation_content admin view will have state change actions.

API changes

No API change only addition.
Adds new moderation state change action and deriver.

Data model changes

None.