[cloud] Add check mode for cloudformation module (#23483)
[cloud] Add check mode for cloudformation module (#23483)

* cloudformation: dummy check mode

* cloudformation: use changesets to implement check mode

* cloudformation: wait at most 5min for change set

* cloudformation: handle stack creation and deletion in check mode

* cloudformation: standardize output format in check mode

msg is a string, meta is a list

* cloudformation: use same naming convention in get_changeset as create_changeset

also add comment about code duplication between said functions

* Remove unused imports

* PEP8 whitespace fix

* Fix CI, convert success=True check to for/else

thaim/ansible,thaim/ansible