Bulk migration to fail_json_aws (ansible-collections#361)

* Split imports and sort
* Move camel_dict_to_snake_dict imports to ansible.module_utils.common.dict_transformations
* Cleanup unused imports
* Bulk migration to fail_json_aws
* Changelog

This commit was initially merged in https://github.com/ansible-collections/community.aws
See: ansible-collections/community.aws@6c88315

plugins/modules/iam_policy_info.py

@@ -77,16 +77,13 @@
     type: list
 '''
 
-import json
-
 try:
     from botocore.exceptions import BotoCoreError, ClientError
 except ImportError:
     pass
 
 from ansible_collections.amazon.aws.plugins.module_utils.core import AnsibleAWSModule
 from ansible_collections.amazon.aws.plugins.module_utils.ec2 import AWSRetry
-from ansible.module_utils.six import string_types
 
 
 class PolicyError(Exception):