Add --os=all and --arch=all options for brew audit.

[reitermarkus]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

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Needs to be rebased onto #15201.

[MikeMcQuaid]

This is looking good so far! I have to be honest and say that I haven't given every line detailed review. Is there any way to split this into multiple, smaller PRs for review before merge?

Similarly, I have mild concerns with the amount of code that's not covered by any tests but want to avoid adding new integration tests for all these commands. Suggestions welcome, may not be blocking.

Thanks again @reitermarkus, great work here.

[MikeMcQuaid]

Looking good! A few questions and thoughts here but nothing major. Nice work @reitermarkus!

[MikeMcQuaid]

One style nit if you can be bothered but fine if this ships as-is. Thanks again @reitermarkus!