Add Ruby 3.4.0-preview2 support for github workflow tests

[sarahchen6]

What does this PR do?
This PR adds Ruby 3.4.0-preview2 support for github workflow tests, specifically macos and yjit, by adding a "3.4" version to the test-yjit.yaml and test-macos.yml files under .github. It also updates the Dockerfile-3.4.0 base image to ruby:3.4.0-preview2 and adjusts a few of the spec tests, given new Ruby output changes (see here).

Motivation:
Though the official Ruby 3.4 is not yet released, we can temporarily add Ruby 3.4.0-preview2. This allows us to start testing with Ruby 3.4 in our CI and spot -> address issues early. After Ruby 3.4 is officially released post-Dec 25, 2024, we can replace the preview with it.

Change log entry
No change log entry for now. Thinking to have a "Ruby 3.4.0-preview2 support added" update after it is fully supported.

Additional Notes:
More Ruby 3.4.0-preview2 support is needed. This PR is one step toward full support and only addresses github workflow tests. It acts alongside #4038 .

How to test the change?
This change can be tested in CI.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (25d6fb8) to head (eb944e7).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4039      +/-   ##
==========================================
- Coverage   97.73%   97.72%   -0.02%     
==========================================
  Files        1338     1338              
  Lines       80249    80252       +3     
  Branches     4016     4017       +1     
==========================================
- Hits        78434    78424      -10     
- Misses       1815     1828      +13     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2024-11-06 16:03:51

Comparing candidate commit eb944e7 in PR branch sarahchen6/add-ruby-3.4-github with baseline commit 2fae103 in branch master.

Found 1 performance improvements and 1 performance regressions! Performance is the same for 27 metrics, 2 unstable metrics.

scenario:method instrumentation

• 🟥 throughput [-10656.663op/s; -10062.636op/s] or [-5.825%; -5.500%]

scenario:profiler - gvl benchmark samples

• 🟩 throughput [+618.533op/s; +627.675op/s] or [+5.524%; +5.605%]