Create individually namespace args for each command

[dduugg]

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As a follow-up to #16814 this PR makes the args for each command individually namespace. The advantages include a browsable API (have a look at https://rubydoc.brew.sh/Homebrew/CLI/Args.html before this goes in 😬), better type annotations (some commands define the same arg under different conditions), better type-checking (referencing an arg from another command will result in an error).

To do this, an Args class under the commands namespace is dynamically created when cmd_args is evaluated. This lets us implement this change without breaking the command API, though it does introduce a fair amount of Ruby magic.

(The first commit does the heavy lifting, the second applies it with brew tc --update.)

(Opening in draft mode for initial feedback.)

[apainintheneck]

I like this approach. It makes sense to me.

[MikeMcQuaid]

Love the approach! Nice work @dduugg!

[dduugg]

Opening up for general review. On re-reading, I'm actually pleasantly surprised how easy this was to wire up (~5 lines of runtime code).

[MikeMcQuaid]

Approving again and merging, thanks @dduugg!