Incorporate the Storage Buckets API once it becomes standardized

[a-sully]

For now, this spec only refers to a Storage Buckets in non-normative text. For example, there's text like this:

|locator|'s [=file system locator/root=] might include relevant identifying information such as the [=storage bucket=]

Once Storage Buckets becomes standardized, we can make it explicit that a file system locator knows about its storage bucket if it's in an Origin Private File System (or whatever we decide to call it #92), which would be a much cleaner solution to #103

[a-sully]

Apologies, I confused the incubating Storage Buckets API with the already-specified storage bucket concept. We can do this now