[NO-TICKET] Fix flaky profiler object counting spec

[ivoanjo]

What does this PR do?

This PR fixes the following flaky profiler spec
(seen in
https://app.circleci.com/pipelines/github/DataDog/dd-trace-rb/19126/workflows/00361a70-d216-4fa9-9ce9-0f87e5f033f1/jobs/669239):

Failures:

  1) Datadog::Profiling::Collectors::CpuAndWallTimeWorker._native_allocation_count when CpuAndWallTimeWorker has been started when allocation profiling and allocation counting is enabled returns different numbers of allocations for different threads
     Failure/Error: expect(after_t1 - before_t1).to be 100

       expected #<Integer:201> => 100
            got #<Integer:217> => 108

       Compared using equal?, which compares object identity,
       but expected and actual are not the same object. Use
       `expect(actual).to eq(expected)` if you don't care about
       object identity in this example.
     # ./spec/datadog/profiling/collectors/cpu_and_wall_time_worker_spec.rb:1377:in `block (5 levels) in <top (required)>'
     # ./spec/spec_helper.rb:238:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:123:in `block (2 levels) in <top (required)>'
     # /usr/local/bundle/gems/webmock-3.23.0/lib/webmock/rspec.rb:39:in `block (2 levels) in <top (required)>'
     # /usr/local/bundle/gems/rspec-wait-0.0.9/lib/rspec/wait.rb:46:in `block (2 levels) in <top (required)>'

We had previously debugged the same issue on another spec in #3554 (and left a nice comment explaining what the issue is).

I just propagated the same fix (disabling GC for the duration of the test) to this spec as well.

Motivation:

Zero known flaky profiler tests!

Change log entry

Nope

Additional Notes:

In practice what happens is that we're counting how many Ruby objects get created during the spec, but if GC gets triggered at the exact wrong time, it may trigger other Ruby code running, and thus more objects than expected being allocated.

By disabling GC for this test, hopefully we're able to keep the Ruby VM from not allocating any incidental things in the background.

This GC counting feature is also deprecated, so in the future we'll remove it which is even nicer :)

How to test the change?

Validate that CI is still green.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: ivoanjo/fix-profiling-flaky-spec
Commit report: 8f52c60
Test service: dd-trace-rb

✅ 0 Failed, 22040 Passed, 1478 Skipped, 5m 53.1s Total Time

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (fba70fd) to head (8f52c60).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4362      +/-   ##
==========================================
- Coverage   97.73%   97.72%   -0.01%     
==========================================
  Files        1347     1347              
  Lines       82388    82389       +1     
  Branches     4193     4193              
==========================================
- Hits        80522    80518       -4     
- Misses       1866     1871       +5     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-10 18:28:08

Comparing candidate commit 8f52c60 in PR branch ivoanjo/fix-profiling-flaky-spec with baseline commit fba70fd in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.