Correctly handle bundler 4 being available

[Earlopain]

On actions that run against ruby-dev, it currently prints the following output (example workflow):

Using Bundler 2 shipped with ruby-head

But ruby-head ships with bundler 4. There is also the following deprecation from bundler:

[DEPRECATED] Using the config command without a subcommand [list, get, set, unset] is deprecated and will be removed in the future. Use bundle config set --local path /home/runner/work/rubocop/rubocop/vendor/bundle instead.

There is a bit of code to handle bundler 1/2 for a variety of different configurations already, so I won't open a PR for this. It's a bit too complicated to really understand what is going on for me

[Petercopter]

Bundler 4 was released today and I'm seeing the same message with Ruby 3.4.7

/opt/hostedtoolcache/Ruby/3.4.7/x64/bin/bundle config --local path /home/runner/work/projectname/projectname/vendor/bundle
[DEPRECATED] Using the `config` command without a subcommand [list, get, set, unset] is deprecated and will be removed in the future. Use `bundle config set --local path /home/runner/work/projectname/projectname/vendor/bundle` instead.

[eregon]

There is a bit of code to handle bundler 1/2 for a variety of different configurations already, so I won't open a PR for this. It's a bit too complicated to really understand what is going on for me

It's not that complicated IMO, but sure I can take care of that.

[eregon]

Not that simple either, I'll admit, due to numerous Bundler/RubyGems bugs we have to work around and required_ruby_version not working for many Ruby / RubyGems versions:
#832

[eregon]

Use bundle config set --local path /home/runner/work/rubocop/rubocop/vendor/bundle instead.

Argh, on Bundler 1 bundle config set --local path foobar results in setting BUNDLE_SET: "--local path foobar" in ~/.bundle/config, so not local and not the correct value :/
And bundle config --local set path foobar results in setting BUNDLE_SET: "path foobar" in .bundle/config, so local but not correct value.

[Petercopter]

👍 @eregon thank you!