Address sucker_punch flaky test

[sarahchen6]

What does this PR do?
This PR avoids a concurrency issue in sucker_punch tests by retrieving the length of the span arrays.

Motivation:
Minimize our flaky tests! Per Ivo's comment below, the issue was caused by traces.collect(&:spans) in the original fetch_spans call. The rspec thread was reading the span arrays in TraceSegment#spans at the same time as the sucker_punch thread was mutating them. This created flakiness with occasional concurrency issues. Since the sucker_punch tests only require span counts, we can instead specifically retrieve the array lengths, which avoids reading (and iterating) through the span arrays like before.

This PR addresses: https://github.com/DataDog/ruby-guild/issues/186.

Change log entry
No.

Additional Notes:
N/A

How to test the change?
Hope to never see this bug again in CI... I tested the flakiness by running the test 1000 times in a row without failure.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: sarahchen6/attempt_suckerpunch_flaky_test
Commit report: e02ad49
Test service: dd-trace-rb

✅ 0 Failed, 22011 Passed, 1476 Skipped, 6m 23s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-07 16:32:19

Comparing candidate commit e02ad49 in PR branch sarahchen6/attempt_suckerpunch_flaky_test with baseline commit 6b6ec18 in branch master.

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (6b6ec18) to head (e02ad49).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4344      +/-   ##
==========================================
- Coverage   97.73%   97.72%   -0.02%     
==========================================
  Files        1347     1347              
  Lines       82349    82351       +2     
  Branches     4187     4187              
==========================================
- Hits        80486    80478       -8     
- Misses       1863     1873      +10     

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[ivoanjo]

Looks reasonable! Any reason for this to still be marked as draft? :)

[ivoanjo]

👍 LGTM. Ahaha one of those PRs that looks deceptively simple after all the work we poured into making it simple :D

[ivoanjo]

👍 LGTM. Ahaha one of those PRs that looks deceptively simple after all the work we poured into making it simple :D