Move integration testing code to its own crate

[khieta]

Describe the improvement you'd like to request

Currently the integration test format and related code is defined in the cedar-policy crate, which makes it difficult to refactor testing code without making breaking changes. We should move all of this to a separate crate (e.g., in the cedar-integration-tests folder) in the next major version of Cedar.

Describe alternatives you've considered

No response

Additional context

No response

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this internal improvement
• ⚠️ This feature might incur a breaking change

[khieta]

Created a new testing crate in #707. Will leave this issue open until the old integration testing code is removed.

[john-h-kastner-aws]

Linking this with #820. Maybe even worth closing this if all remaining work is covered by that issue?

[khieta]

They're closely related -- this issue is to delete the cedar-policy/integration_testing.rs file and #820 is to delete the cedar-integration-tests/ folder.

I'll close this issue & add a note to the other. The more issues I leave open, the more I'll forget to close later 😅