Delete the `cedar-integration-tests` folder

[khieta]

Describe the improvement you'd like to request

Now that the integration tests have a new home (https://github.com/cedar-policy/cedar-integration-tests), we should delete the the local (outdated) cedar-integration-tests folder.

This is currently blocked by cedar-java#130. All other repositories (cedar, cedar-spec, cedar-go) have been migrated to the new tests. Hopefully this issue can be addressed once we've completed #757.

Edit: We should also delete the cedar-policy/integration_testing.rs file, the contents of which were deprecated in #707.

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

[cdisselkoen]

The relevant part of #757 was covered in #793, so I think the only work needed is cedar-policy/cedar-java#130 and then actually updating the Java integration tests to point at the new folder.