Fixes
- Fix rule [W2501](https://github.com/aws-cloudformation/cfn-python-lint/blob/main/docs/rules.md#W2501) to support dashes in KMS Key name
- Fix rule [E2543](https://github.com/aws-cloudformation/cfn-python-lint/blob/main/docs/rules.md#E2543) to not fail when the type of a step isn't known
- Fix rule [E2507](https://github.com/aws-cloudformation/cfn-python-lint/blob/main/docs/rules.md#E2507) to have an exception for ECR Policies. Resource isn't required.
- Several Python cleanup items around initializing lists, how version is loaded, and dropping 'discover' in testing