DEBUG-3182 DI: remove hard dependency on tracing

[p-datadog]

What does this PR do?

Removes hard dependency of DI on Tracing.

• Existing requires of tracing components from DI removed
• DI will check if Datadog::Tracing exists before referencing current_span & current_trace
• Unit tests adjusted to require their dependencies explicitly and to use local CodeTracker instances rather than the global one

Motivation:

DI code tracker must be loaded early in application boot process. Tracing must be loaded late to instrument third-party libraries. Currently, DI requires some tracing components which may result in tracing not loading correctly.

Change log entry

None - I am currently not aware of specific issues with DI or tracing loading.

Additional Notes:

I intend to add a test in a separate PR that loads DI code tracking in a forked process, verifies that the code tracking works correctly, and asserts that none of the other components (most importantly tracing but we could check others too) have been loaded.

How to test the change?

I tested the encapsulation manually by removing a bunch of requires pertaining to tracing from spec_helper.rb and other helpers. The main test of the DI code tracker both working correctly and not loading tracing will be in a later PR.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: di-undepend-tracing
Commit report: f0accc9
Test service: dd-trace-rb

✅ 0 Failed, 22103 Passed, 1457 Skipped, 5m 28.75s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-12-12 18:46:44

Comparing candidate commit f0accc9 in PR branch di-undepend-tracing with baseline commit 65fb81d 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

Attention: Patch coverage is 93.33333% with 3 lines in your changes missing coverage. Please review.

Project coverage is 97.75%. Comparing base (65fb81d) to head (f0accc9).

Files with missing lines	Patch %	Lines
lib/datadog/di/probe_notification_builder.rb	71.42%	2 Missing ⚠️
spec/datadog/di/spec_helper.rb	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4223      +/-   ##
==========================================
- Coverage   97.75%   97.75%   -0.01%     
==========================================
  Files        1355     1355              
  Lines       82165    82189      +24     
  Branches     4207     4213       +6     
==========================================
+ Hits        80321    80344      +23     
- Misses       1844     1845       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[marcotc]

I agree with @ivoanjo's point here, but overall awesome work!