DEBUG-3210 DI: change logging to be appropriate for customer inspection

[p-datadog]

Replaces #4230

What does this PR do?

Changes logging levels used in DI:

• Failure to enable DI is now a warning (since enabling it must have been requested by the customer).
• Remaining logging calls are now emitted at debug level, making those entries not visible in customer logs.

All log messages have datadog: di: prefix to make it easy for customers to understand what is generating them.

Motivation:

DI currently uses the logger for reporting its internal issues. However, the logger normally logs to customer logs, and as such the default logging should be customer-centric, meaning log entries should only be created for matters that the customers understand and can fix.

Change log entry

Dynamic instrumentation: logging of internal conditions is now done on debug level, and these log entries will not be visible by default in customer applications.

Additional Notes:

I attempted to use block form of logger calls to delay string interpolation until the logging actually happens, but this made my logging assertions fail in the test suite. Since the logging should be very infrequent I kept the calls as they were (pre-interpolated).

How to test the change?

Due to the introduction of an additional layer of abstraction for DI logging, end-to-end tests will need to have additional assertions added for log entries being visible (or not). This will be done as part of DEBUG-3210 but is not part of this PR.

[github-actions]

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^{Visited at: 2025-01-08 15:43:23 UTC}

[datadog-datadog-prod-us1]

Datadog Report

Branch report: di-logger-2
Commit report: af7282b
Test service: dd-trace-rb

✅ 0 Failed, 22132 Passed, 1476 Skipped, 5m 9.15s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-08 19:22:10

Comparing candidate commit af7282b in PR branch di-logger-2 with baseline commit e3ea38f 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 68.08511% with 15 lines in your changes missing coverage. Please review.

Project coverage is 97.73%. Comparing base (9440c03) to head (af7282b).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/datadog/di/component.rb	42.85%	4 Missing ⚠️
lib/datadog/di/probe_notifier_worker.rb	0.00%	4 Missing ⚠️
lib/datadog/di/instrumenter.rb	25.00%	3 Missing ⚠️
lib/datadog/di/probe_manager.rb	50.00%	2 Missing ⚠️
lib/datadog/di/code_tracker.rb	0.00%	1 Missing ⚠️
spec/datadog/di/spec_helper.rb	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4266      +/-   ##
==========================================
- Coverage   97.73%   97.73%   -0.01%     
==========================================
  Files        1352     1352              
  Lines       82409    82424      +15     
  Branches     4224     4232       +8     
==========================================
+ Hits        80545    80557      +12     
- Misses       1864     1867       +3     

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[ivoanjo]

Left a few notes + I had left a few extra text suggestion improvements on the earlier #4230 .

[p-datadog]

I did also apply the wording suggestions, they got reverted but now are reinstated.