Improvements to JSON bottle handling

[Rylan12]

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Follow-up to #11648

This PR does three things to improve the way JSON bottles are handled:

1. BottleAPI::fetch_bottles only downloads dependency bottles if no up-to-date version of the formula is installed locally. This means we don't need to spend time downloading bottles for all dependencies if they will never be used.
2. Automatic Homebrew updates (i.e. brew update --preinstall), no longer fetches homebrew/core (as long as HOMEBREW_JSON_CORE is set). Running brew update manually will still fetch homebrew/core.
3. brew info now shows the most recent version information if HOMEBREW_JSON_CORE is set rather than the version that exists in the tap.

[BrewTestBot]

Review period will end on 2021-07-15 at 06:41:12 UTC.

[MikeMcQuaid]

All makes sense to me! Some comments but optional and can be in a follow-up PR if desired.

[BrewTestBot]

Review period skipped due to critical label.

[Rylan12]

When playing around locally I realized that :all bottles were not supported, so I added support in this PR