Allow clipboard permissions in editor iframe

[kevin940726]

Related to #74542

Proposed Changes

Add clipboard-read and clipboard-write to the allow list of the editor iframe. Right now, only clipboard-read is required for #74542, but we might want to add more features related to the clipboard in the future, so I also added clipboard-write.

Note that adding them to the allow list doesn't automatically grant these permissions for the users, Users still have to explicitly allow them when asked. Without the allow list, users won't be asked at all (for cross-origin iframes).

Testing Instructions

I'm not sure how to test it, unfortunately. But #74542 should contain the necessary steps to test it.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?

[matticbot]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-61768

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-61768&env=jetpack

[mattwiebe]

I can confirm that this allows clipboard permissions to function properly in that permission is requested by Chrome and copy and paste works properly after that.