[CIVIS-8552] ci-queue support for rspec

[anmarchenko]

What does this PR do?
Fix #96

Adds RSpec instrumentation support when running with ci-queue test runner. It instruments RSpec::Queue::Runner that is used by ci-queue and also creates "single-test" test suite akin to Minitest parallel tests if we detect to be running in a RSpec::Core::Example instrumented by ci-queue. Also it fixes our handling of pending tests correctly marking them as skipped and adds a lot of unit tests around all of the ways we can skip tests in RSpec

Motivation
We have users of this library who run their rspec test suites using ci-queue

[codecov-commenter]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (c3ccfee) 99.06% compared to head (1d7d3ac) 98.96%.

Files	Patch %	Lines
...c/datadog/ci/contrib/rspec/instrumentation_spec.rb	93.20%	7 Missing ⚠️
lib/datadog/ci/contrib/rspec/example.rb	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #112      +/-   ##
==========================================
- Coverage   99.06%   98.96%   -0.11%     
==========================================
  Files         149      151       +2     
  Lines        6308     6469     +161     
  Branches      288      299      +11     
==========================================
+ Hits         6249     6402     +153     
- Misses         59       67       +8     

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