You need both an action pluginaction plugin and an action config entity using that plugin for views to expose the bulk action field on entity types. Create thataction config entity
- Create the plugin with drush:
drush generate plugin-action
- Create the action config entity: look at "system.action.comment_delete_action.yml" for an example.
After creating these, then clear the cache and it should be available in views under the label "Bulk update".