Require an argument to --bottle-tag in fetch and --cache

[Rylan12]

Fixes #13484

This PR requires that an argument is passed to --bottle-tag in brew fetch and brew --cache. Now, running these commands on their own will fail immediately:

$ brew fetch wget --bottle-tag
Error: missing argument: --bottle-tag

$ brew --cache wget --bottle-tag
Error: missing argument: --bottle-tag

[BrewTestBot]

Review period skipped due to critical label.

[MikeMcQuaid]

Nice work!

[NlightNFotis]

Nice, thank you for fixing this so quick!

Question - do you have any sort of tests for this? For example, regex-based tests on the output to make sure that the error message is emitted correctly and no regressions are introduced at a later point?

[Rylan12]

Question - do you have any sort of tests for this?

Yes, here