Create client for EventPolicy

[creydr]

To work with the EventPolicy type (#7971), we need to add a new client. This should be doable by adding

// +genclient

to the EventPolicy type and running ./hack/update-codegen.sh.

Prerequisites:

• Add EventPolicy type #7971

Additional Information:

• Check for example on the Broker type, how the client was added

Additional hints for new contributors before starting with this issue:

1. When the issue has the Draft status, the issue is subject to change and thus should not be started to be worked on
2. Make sure you've read and understood the CONTRIBUTING.md guidelines
3. Make sure you're able to run Knative Eventing locally and run at least the unit tests.
4. When you feel comfortable with this issue, feel free to assign it to you (e.g. by commenting /assign) and ask any question you have. Please be aware that we might unassign you, if we don't see any progress from your side to give other contributors also a chance to work on this issue.

[creydr]

Closing this as we included this in #7971