Patch io-event gem to drop epoll_pwait2 check for RedHat 9

What does this MR do?

Some distributions (e.g. RedHat 9.7) ship glibc 2.34 with backported epoll_pwait2 support tagged as GLIBC_2.35, causing binaries built there to fail on systems with a true glibc 2.34 (RedHat 9.6).

This change:

• Adds a new ruby-io-event software definition that rebuilds the io-event gem without the epoll_pwait2 check on RedHat 9 systems.
• Adds the ruby-io-event dependency to the gitlab project for RedHat 9.
• Adds a el_9? helper method to OhaiHelper for platform detection

https://github.com/socketry/io-event/pull/159 would avoid the need for this patching.

Relates to https://gitlab.com/gitlab-com/request-for-help/-/work_items/4332

Related issues

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