Use timeout.rb from upstream

[eregon]

Currently we have a custom version in https://github.com/oracle/truffleruby/blob/90bfaa00401778f11849dbca05eb1bd008271c1b/lib/truffle/timeout.rb.
But now that upstream (the gem, and also the version shipped in 3.2) also avoids creating a thread per Timeout.timeout call, there is no much reason to use our custom timeout.rb, and in fact it would be more compatible to use upstream.

[olleolleolle]

👋 Hi! I recently looked at the CI run on the upstream repo. The job truffleruby-head on ubuntu-latest took a while (>26 minutes) to do anything in the step that executes the tests. https://github.com/ruby/timeout/actions/runs/10595331126/job/29360878189

The step is...
bundle exec rake test

Got ideas on what's going on? The macos-latest seem to be done in 5s.

(If you wish to shunt this Issue comment to its own something, Discussion, Issue, comment thread in the ruby/timeout repo, please shunt away.)

[eregon]

@olleolleolle I moved your comment to a new issue: #3652 since it's unrelated.