When using OOTB CFN Test is broken with 'Tags' attribute on generated class

Assuming same steps in https://github.com/aws-cloudformation/cloudformation-cli-python-plugin/issues/247, using the workaround to get by the current cryptography issue.

After trying to run one test `cfn test -- -k contract_create_delete`, it fails with:
```
Traceback (most recent call last):
File "/var/task/cloudformation_cli_python_lib/resource.py", line 165, in _cast_resource_request
return UnmodelledRequest(
File "/var/task/cloudformation_cli_python_lib/utils.py", line 156, in to_modelled
desiredResourceState=model_cls._deserialize(self.desiredResourceState),
File "/var/task/dd_dd_dd/models.py", line 74, in _deserialize
Tags=set_or_none(json_data.get("Tags")),
File "/var/task/dd_dd_dd/models.py", line 30, in set_or_none
return set(value)
TypeError: unhashable type: 'dict'
```

Root cause and fix:

- The default JSON makes Tags a list/array of Tag object (`"#/definitions/Tag"`). A tag object then has a key and value attribute. This is not hashable
- Fix(probably) change [this line](https://github.com/aws-cloudformation/cloudformation-cli-python-plugin/blob/master/python/rpdk/python/templates/models.py#L30) to a frozen set: `return frozenset(value)`
- Also same change for [hooks](https://github.com/aws-cloudformation/cloudformation-cli-python-plugin/blob/master/python/rpdk/python/templates/hook_models.py#L27)?
- Maybe [this](https://github.com/aws-cloudformation/cloudformation-cli-python-plugin/blob/master/python/rpdk/python/templates/target_model.py#L27) one too.