Exposes policy effect for static policies and templates

[muditchaudhary]

Description of Changes

This PR adds functionality to expose the effect of Cedar policies, aligning with the capabilities available in Cedar Rust's Policy and Template implementations.

Changes

• Implements effect() method to determine if a policy is a "permit" or "forbid" policy
• Exposes effect for both static policies and templates
• Adds unit tests

Implementation Note

Cedar Java currently uses a unified Policy class for both static policies and templates, unlike Cedar Rust which separates these concerns into distinct Policy and Template structs. To maintain compatibility while exposing this functionality:

1. The effect() method first attempts to parse the input as a static policy and gets the effect
2. If getting the effect as static policy fails, it attempts to parse as a template
3. Returns the appropriate effect based on the successful parse

Future Considerations

Refactor Cedar Java to mirror Cedar Rust's separation of Policy and Template into distinct classes, allowing for better handling of each policy type.