Ruby 3 working branch

[Bo98]

Tests for Ruby 3.2.

What I plan for this branch:

• This will be rebased as necessary until all builds pass and the "TEMP: workflow workarounds for ruby3 branch" commit is no longer required (i.e. brew itself supports handling of Ruby 3 gems).
• At that point, I'll make it a protected branch and we can make releases from that branch that we can use in brew.
• When Ruby 2.6 is killed (i.e. we are sure we will never need to make another Portable Ruby 2.6 release again), then this PR can be merged.

Don't really want to faff around with versioned formulae and adjusting all the workflows to build twice when branches work fine for this purpose, are simpler and make the diff easier to follow.

[EricFromCanada]

Off-topic: are .humanize and .titleize in Abstract/portable-formula.rb vestigial remains of an older way of handling macOS version names? They don't seem to be defined anywhere.

[Bo98]

They were ActiveSupport stuff removed with https://github.com/Homebrew/brew/pull/14778. The code here just never got updated, nor is it a code path CI covers.

I suppose that's a problem shared with all of the ActiveSupport extensions - they're not explicitly a part of our public API but some are highly used regardless in homebrew-core etc.

[Bo98]

This is probably ready to tag a release on and to add an opt-in within brew.

I could either tag a release as "3.1.4-rc.homebrew1" or just do "3.1.4" and revision bump if it ends up having issues. I don't anticipate any though and will test a bit locally.

[SMillerDev]

Let's keep it in line with the normal versions and do rev bumps if needed

[MikeMcQuaid]

Agreed. Let's version this normally and then can make it HOMEBREW_DEVELOPER only for some Homebrew/brew testing and then get it early on a tag for testing before stable branch folks.

[Bo98]

HOMEBREW_RUBY3 🔜

(today)