[PROF-6559] Mark Ruby CPU Profiling 2.0 as being in beta

[ivoanjo]

What does this PR do?:

This PR collects a few small changes needed before releasing the new Ruby profiler bits ("CPU Profiling 2.0") as opt-in (that is, disabled by default) public beta.

I recommend reviewing commit-by-commit.

Motivation:

We're finally ready to start telling customers they can enable this new mode.

Additional Notes:

(N/A)

How to test the change?:

Change includes test coverage (the little code that is affected).

[codecov-commenter]

Codecov Report

Merging #2489 (91cc4c5) into master (ec7b868) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2489   +/-   ##
=======================================
  Coverage   98.32%   98.32%           
=======================================
  Files        1118     1120    +2     
  Lines       60351    60401   +50     
=======================================
+ Hits        59339    59390   +51     
+ Misses       1012     1011    -1     

Impacted Files	Coverage Δ
lib/datadog/core/configuration/components.rb	98.92% <ø> (ø)
...tadog/profiling/collectors/idle_sampling_helper.rb	93.54% <ø> (ø)
spec/datadog/core/configuration/components_spec.rb	100.00% <ø> (ø)
lib/datadog/profiling.rb	100.00% <100.00%> (ø)
...adog/profiling/collectors/dynamic_sampling_rate.rb	100.00% <100.00%> (ø)
...profiling/collectors/dynamic_sampling_rate_spec.rb	100.00% <100.00%> (ø)
spec/datadog/profiling/native_extension_spec.rb	98.11% <0.00%> (-0.63%)	⬇️
...ng/contrib/active_support/cache/instrumentation.rb	87.67% <0.00%> (+0.08%)	⬆️
lib/datadog/core/diagnostics/environment_logger.rb	99.21% <0.00%> (+0.78%)	⬆️
lib/datadog/core/workers/polling.rb	100.00% <0.00%> (+3.44%)	⬆️

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