[CIVIS-9478] Knapsack Pro 7/RSpec 3 support

[anmarchenko]

Closes #147

What does this PR do?
Adds instrumentation to KnapsackPro::Runners::Queue::RSpecRunner for knapsack_pro gem versions 7.0 and above. This makes sure that every knapsack_pro run is correctly reported to Datadog as a separate test session.

Motivation
Multiple reports of Datadog dropping test spans when using knapsack_pro

How to test the change?
Unit tests are provided

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 97.72727% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 98.97%. Comparing base (59a92c8) to head (88ec42e).

Files	Patch %	Lines
...ib/datadog/ci/contrib/rspec/knapsack_pro/runner.rb	92.85%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #172      +/-   ##
==========================================
- Coverage   98.98%   98.97%   -0.02%     
==========================================
  Files         198      202       +4     
  Lines        9638     9726      +88     
  Branches      423      431       +8     
==========================================
+ Hits         9540     9626      +86     
- Misses         98      100       +2     

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[pcothenet]

@anmarchenko Previously, we had c.ci.force_test_level_visibility = true to work with Knapsack Pro. Should we drop this setting when testing this Beta?

[anmarchenko]

@pcothenet yes, drop force_test_level_visibility from now on - knapsack pro is supported now

[connorshea]

Does this also work for minitest?

[anmarchenko]

@connorshea I didn't test support for minitest with knapsack pro; but it might still work. Please try it and create an issue if it doesn't work.