chore(tracing): remove atexit dead code and forksafe dead code

[ZStriker19]

In python 3.7 (what we support currently on main) hasattr(atexit, "unregister") is always true, so we don't need to check it. hasattr(os, "register_at_fork") is also ways true, so we don't need to check it.

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.
• If change touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.

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: zachg/clean_up_old_code_paths_for_exit_and_fork
Commit report: 98a8724
Test service: dd-trace-py

✅ 0 Failed, 170515 Passed, 1045 Skipped, 10m 32.39s Wall Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-03-04 17:28:11

Comparing candidate commit 0934f71 in PR branch zachg/clean_up_old_code_paths_for_exit_and_fork with baseline commit 688074a in branch main.

Found 17 performance improvements and 14 performance regressions! Performance is the same for 172 metrics, 9 unstable metrics.

scenario:coreapiscenario-context_with_data_listeners

• 🟩 max_rss_usage [-902.854KB; -737.184KB] or [-3.010%; -2.457%]

scenario:coreapiscenario-context_with_data_no_listeners

• 🟩 max_rss_usage [-767.796KB; -606.412KB] or [-2.563%; -2.024%]

scenario:coreapiscenario-context_with_data_only_all_listeners

• 🟥 max_rss_usage [+892.647KB; +1065.650KB] or [+3.084%; +3.681%]

scenario:coreapiscenario-core_dispatch_listeners

• 🟩 max_rss_usage [-790.389KB; -605.938KB] or [-2.638%; -2.023%]

scenario:coreapiscenario-core_dispatch_listeners_and_all_listeners

• 🟩 max_rss_usage [-1.126MB; -0.984MB] or [-3.750%; -3.276%]

scenario:coreapiscenario-core_dispatch_no_listeners

• 🟩 max_rss_usage [-786.783KB; -636.577KB] or [-2.626%; -2.124%]

scenario:coreapiscenario-core_dispatch_only_all_listeners

• 🟩 max_rss_usage [-800.463KB; -622.897KB] or [-2.673%; -2.080%]

scenario:coreapiscenario-core_dispatch_with_results_listeners

• 🟥 max_rss_usage [+0.946MB; +1.095MB] or [+3.268%; +3.785%]

scenario:coreapiscenario-core_dispatch_with_results_no_listeners

• 🟩 max_rss_usage [-838.051KB; -669.686KB] or [-2.795%; -2.233%]

scenario:coreapiscenario-get_item_missing

• 🟩 max_rss_usage [-854.039KB; -662.300KB] or [-2.848%; -2.209%]

scenario:coreapiscenario-set_item

• 🟩 max_rss_usage [-784.924KB; -615.499KB] or [-2.619%; -2.054%]

scenario:httppropagationextract-all_styles_all_headers

• 🟥 max_rss_usage [+664.492KB; +788.360KB] or [+2.265%; +2.688%]

scenario:httppropagationextract-b3_headers

• 🟩 max_rss_usage [-1003.927KB; -904.809KB] or [-3.336%; -3.007%]

scenario:httppropagationextract-b3_single_headers

• 🟥 max_rss_usage [+698.634KB; +811.970KB] or [+2.385%; +2.772%]

scenario:httppropagationextract-invalid_priority_header

• 🟩 max_rss_usage [-802.971KB; -682.648KB] or [-2.669%; -2.269%]

scenario:httppropagationextract-tracecontext_headers

• 🟩 max_rss_usage [-822.040KB; -714.779KB] or [-2.731%; -2.375%]

scenario:httppropagationextract-wsgi_empty_headers

• 🟥 max_rss_usage [+638.132KB; +766.796KB] or [+2.174%; +2.612%]

scenario:httppropagationextract-wsgi_invalid_priority_header

• 🟥 max_rss_usage [+660.348KB; +778.167KB] or [+2.254%; +2.656%]

scenario:httppropagationextract-wsgi_invalid_span_id_header

• 🟥 max_rss_usage [+675.189KB; +771.928KB] or [+2.303%; +2.633%]

scenario:httppropagationextract-wsgi_large_header_no_matches

• 🟩 max_rss_usage [-814.117KB; -723.521KB] or [-2.706%; -2.405%]

scenario:httppropagationextract-wsgi_medium_header_no_matches

• 🟩 max_rss_usage [-788.102KB; -674.989KB] or [-2.621%; -2.244%]

scenario:httppropagationextract-wsgi_valid_headers_all

• 🟥 max_rss_usage [+631.853KB; +740.717KB] or [+2.148%; +2.518%]

scenario:httppropagationinject-with_all

• 🟩 max_rss_usage [-730.232KB; -659.541KB] or [-2.435%; -2.199%]

scenario:otelspan-start

• 🟩 max_rss_usage [-5.074MB; -4.733MB] or [-10.142%; -9.461%]

scenario:samplingrules-average_match

• 🟩 max_rss_usage [-720.509KB; -606.595KB] or [-2.403%; -2.023%]

scenario:sethttpmeta-no-collectipvariant

• 🟥 max_rss_usage [+635.716KB; +746.684KB] or [+2.147%; +2.522%]

scenario:sethttpmeta-obfuscation-no-query

• 🟥 max_rss_usage [+617.380KB; +725.699KB] or [+2.083%; +2.449%]

scenario:sethttpmeta-obfuscation-send-querystring-disabled

• 🟥 max_rss_usage [+654.710KB; +765.373KB] or [+2.193%; +2.564%]

scenario:sethttpmeta-obfuscation-worst-case-implicit-query

• 🟥 max_rss_usage [+673.783KB; +772.924KB] or [+2.257%; +2.589%]

scenario:sethttpmeta-useragentvariant_not_exists_1

• 🟥 max_rss_usage [+731.269KB; +842.824KB] or [+2.472%; +2.849%]

scenario:span-add-metrics

• 🟥 max_rss_usage [+25.779MB; +25.903MB] or [+65.962%; +66.281%]