[CIVIS-8594] Enable test suite level visibility by default (with killswitch)

[anmarchenko]

What does this PR do?
Deprecates and stops using ci.experimental_test_suite_level_visibility_enabled configuration option making test suite level visibility enabled by default.

Adds killswitch ci.force_test_level_visibility that allows users of this library to (temporarily) revert to test level visibility if any unanticipated issues occur.

Motivation
When Ruby library is generally available we'll use test suite level visibility as default.

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (a21b953) 99.10% compared to head (866e57c) 99.05%.

Files	Patch %	Lines
lib/datadog/ci/configuration/settings.rb	62.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
- Coverage   99.10%   99.05%   -0.05%     
==========================================
  Files         147      147              
  Lines        6269     6276       +7     
  Branches      286      288       +2     
==========================================
+ Hits         6213     6217       +4     
- Misses         56       59       +3     

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