AllNamespaces API Key test is now irrelevant

**Summary**

Kuadrant creates all AuthConfigs in the same namespace where Authorino is running. Therefore we changed default value for `spec.authentication.apiKey.allNamespaces` to `True`. This makes `test_all_namespaces_api_key.py` irrelevant.

Refactor/remove this test and implement one that creates a secret in the same namespace as Authorino.

authorino-standalone is not affected, but needs to be think of when implementing this issue

Start with test_all_namespaces_api_key.py and inspect how the tests create namespaces, AuthConfigs, and secrets. Replace the irrelevant coverage with a case that creates the secret in Authorino's namespace, while checking the authorino-standalone setup for any required distinction. Done means the relevant tests pass and the new case verifies same-namespace API key behavior.

Written by the indexing model from the issue text.