Ruby: Check RBS validity on CI

[tk0miya]

To avoid the regressions of the RBS definition, this adds automatic RBS validation on CI.

This also contains the following changes around RBS:

• Update to RBS-4.0 and Steep-2.0
• Manage types of dependencies via rbs_collection.yaml (see https://github.com/ruby/rbs/blob/master/docs/collection.md)

ref: #1711 (review)

[tk0miya]

Sorry, I'm not sure why ruby-gem:test failed. Is this related to this change?

    1) Failure:
  Engine::EvaluationTest#test_0022_complex real world example [test/engine/evaluation_test.rb:369]:
  Expected snapshot file to exist: 
  test/snapshots/engine/evaluation_test/test_0022_complex_real_world_example_d8e54f09b6cf5d8199c941a30266ede6.txt
  
  2521 runs, 6869 assertions, 1 failures, 0 errors, 70 skips

[marcoroth]

Thank you @tk0miya! 🙏🏼

(The test is flaky on test, I just re-run CI and its green now)