## Summary

This PR fixes the duplication of rules. The DE backend was updated to not allow `immutable` when creating a rule, so this broke the `Duplicate Rule` action as we were creating a new rule with `immutable: false`.

This PR also switches rule duplication over to use the bulk `create` API introduced in elastic#53543, so now we can duplicate multiple rules.

And lastly, this PR removes the limitation of not being able to delete immutable rules. So long as you have the appropriate `write` permissions the delete action is now always available.

![duplicate_batch](https://user-images.githubusercontent.com/2946766/72652638-cee69a00-3944-11ea-9e15-cce3f2b8cefe.gif)


### Checklist

Use ~~strikethroughs~~ to remove checklist items you don't feel are applicable to this PR.

- [ ] ~This was checked for cross-browser compatibility, [including a check against IE11](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility)~
- [x] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/master/packages/kbn-i18n/README.md)
- [ ] ~[Documentation](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#writing-documentation) was added for features that require explanation or tutorials~
- [ ] ~[Unit or functional tests](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility) were updated or added to match the most common scenarios~
- [ ] ~This was checked for [keyboard-only and screenreader accessibility](https://developer.mozilla.org/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility#Accessibility_testing_checklist)~

### For maintainers

- [ ] ~This was checked for breaking API changes and was [labeled appropriately](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#release-notes-process)~
- [ ] ~This includes a feature addition or change that requires a release note and was [labeled appropriately](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#release-notes-process)~