All the modules: Add the `idempotent` attribute

[Andersson007]

SUMMARY

Add the idempotent attribute to all the modules similarly as in https://github.com/ansible-collections/community.crypto/pull/833/files

Thanks to Felix for the great idea

• You can do it through the GH web UI by clicking the Edit button in pages representing modules files under the plugins/modules directory
• Or you could do it locally, see Quick start dev guide: if you consider submitting more complex PRs in future against this and other collections / ansible-core

ISSUE TYPE

• Documentation Report