feat(asm): standalone asm

[gnufede]

Description

This PR allows ASM customers to disable APM, and use only ASM features. To have the full picture, see also #9444 and #9445.

Details

It involves changes when opting out from APM with DD_EXPERIMENTAL_APPSEC_STANDALONE_ENABLED=true and DD_APPSEC_ENABLED=true:

• Doesn't disable Span Processors.
• Rate limiting of APM traces is reduced to minimal levels (1 trace per minute).
• Datadog-Client-Computed-Stats header is sent to the agent so it doesn't compute stats on its end, but they aren't computed on the library side either.
• Disables metric reporting.

Checklist

• Change(s) are motivated and described in the PR description
• Testing strategy is described if automated tests are not included in the PR
• Risks are described (performance impact, potential for breakage, maintainability)
• Change is maintainable (easy to change, telemetry, documentation)
• Library release note guidelines are followed or label changelog/no-changelog is set
• Documentation is included (in-code, generated user docs, public corp docs)
• Backport labels are set (if applicable)
• If this PR changes the public interface, I've notified @DataDog/apm-tees.

Reviewer Checklist

• Title is accurate
• All changes are related to the pull request's stated goal
• Description motivates each change
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Change is maintainable (easy to change, telemetry, documentation)
• Release note makes sense to a user of the library
• Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: gnufede/APPSEC-53002-standalone-asm-billing
Commit report: 4880e0b
Test service: dd-trace-py

✅ 0 Failed, 134478 Passed, 39173 Skipped, 5h 55m 58.19s Total duration (2h 49m 3.77s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-05-29 12:15:10

Comparing candidate commit f88da3d in PR branch gnufede/APPSEC-53002-standalone-asm-billing with baseline commit 05fb6fb in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 209 metrics, 9 unstable metrics.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 11.59420% with 61 lines in your changes missing coverage. Please review.

Project coverage is 10.34%. Comparing base (b93575e) to head (4880e0b).

Files	Patch %	Lines
tests/tracer/test_writer.py	0.00%	15 Missing ⚠️
tests/integration/test_trace_stats.py	0.00%	13 Missing ⚠️
tests/tracer/test_tracer.py	0.00%	13 Missing ⚠️
ddtrace/_trace/tracer.py	27.27%	8 Missing ⚠️
...ests/appsec/integrations/test_gunicorn_handlers.py	0.00%	8 Missing ⚠️
tests/appsec/appsec_utils.py	0.00%	3 Missing ⚠️
ddtrace/internal/writer/writer.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #9211       +/-   ##
===========================================
- Coverage   75.96%   10.34%   -65.62%     
===========================================
  Files        1303     1273       -30     
  Lines      123882   122094     -1788     
===========================================
- Hits        94101    12631    -81470     
- Misses      29781   109463    +79682     

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