Resolve overlapping permissions (e.g. only return `*://*/*` if present)

[fregante]

Optionally, but by default, I think permissions should be resolved. If the user granted:

• https://google.com/*
• *://*/*

The latter will always include the former, so processing both is rarely useful. This is additionally shown by a Chrome issue (which I'm not sure other browsers replicate):

• https://github.com/pixiebrix/pixiebrix-extension/issues/1931

This module could return only *://*/* if found.

If webext-patterns can safely match the former with the latter, then it's easy to drop every overlapping pattern, otherwise I can just handle "all urls" as a special case.