Pycfmodel

Fixes
- Update `CLOUDFORMATION_ACTIONS`
- `StatementCondition` only builds evaluator if `eval` is called.

Improvements
- Add `StatementCondition` class, with a function resolver as a replacement for `ConditionDict`.
Removes
- Removes constants `CONDITION_MODIFIERS` and `CONDITION_FUNCTIONS` from `pycfmodel/constants.py`
- Removes `is_conditional_dict` from `pycfmodel/utils.py`
Fixes
- Update `CLOUDFORMATION_ACTIONS`
- Change Metadata dict values to accept any type.

Fixes
- Fix to ensure all `Statement.Effect` fields are always capitalized
- Update `CLOUDFORMATION_ACTIONS`

Fixes
- Fix to `policy_documents` method on `EC2 VPC Endpoint` resource type for when no policy document is added to the resource.

Additions
- Add `EC2 VPC Endpoint Policy` resource.
Changes
- Update list of all CloudFormation actions.

Additions
- New property `policy_documents` to Resources
- New `model.utils` module
- New helper dataclass: `model.utils.OptionallyNamedPolicyDocument`
Improvements
- Added basic tests for the resources that didn't have
Changes
- `_build_regex` moved to `utils` and renamed to `regex_from_cf_string`
Fixes
- Fixed IAMGroup model