caches global property should not be available in Dedicated/Shared WorkerGlobalScope with {credentials: 'omit'}

[BlobTheKat]

Exposing access to caches with {credentials: 'omit'} could allow an untrusted worker running on a web page to overwrite existing cache entries, where it could inject an arbitrary script that would be run the next time the page is loaded. Such a script would then have not just one-time but permanent access to the page's credentials.

Currently both localStorage and indexedDB are inaccessible for workers with this option, this should also be made the case for caches

[mkruisselbrink]

I agree that all storage APIs should behave the same, so if there are cases where localstorage/indexedDB are not available cache storage probably should be rejecting as well; i.e. opaque origins would be one such case. I'm not sure where this behavior is defined for credentials: omit for indexedDB and localStorage?