Add support for bundler 2.2.25+

[RyanBrushett]

Motivation

Add support for Bundler 2.2.25 and up.
Fix #413

Implementation

• Keep support for < 2.2.25 by leaving that codepath mostly unchanged.
• Use the current version of the materialize method for bundler versions 2.2.25 and up.
• I refactored a bit. If this makes it more confusing, let me know and I can rearrange some things. Also: naming variables is hard.

Tests

• I added a 2.2.22 and 2.2.25 bundler versions to the test matrix, otherwise relying on the tests that were there.

[RyanBrushett]

Sidenote: Do we need the actions to run on Push and PR or would just having it on Push be OK?

[RyanBrushett]

Hmm those tests are passing locally. 👀ing.

[vinistock]

bin/test uses bundle exec to execute tests. I don't think that is picking up the right bundler version. You'd need to change that CI step to be

bundle _${{ bundler_version }}_ exec ...

Also, you don't need quotes in the matrix versions.

[RyanBrushett]

Tidied up! Thanks Vini.

Those same tests are still failing, will keep digging! EDIT: I think a change in smart properties means the test needs a cheeky update. Curious why it isn't failing locally though...
I'm gonna remove the pull_request CI option and leave push. If someone's strongly opposed, I'll tack it back on.

[RyanBrushett]

I'll fix the branch protection and ⛵ .

EDIT actually I'll ⛵ first so I don't block other people by setting branch protection that they can't possibly meet.