chore(tracer): add type annotation for HttpPropagator extract

[rachelyangdog]

Add type annotation for HTTPPropagator extract method.

For Issue: #12737

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, 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

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/propagation/http.py                                             @DataDog/apm-sdk-api-python

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 233 ± 4 ms.

The average import time from base is: 238 ± 5 ms.

The import time difference between this PR and base is: -4.5 ± 0.2 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 2.214 ms (0.95%)

ddtrace.bootstrap.sitecustomize 1.536 ms (0.66%)

ddtrace.bootstrap.preload 1.536 ms (0.66%)

ddtrace.internal.products 1.536 ms (0.66%)

ddtrace.internal.remoteconfig.client 0.697 ms (0.30%)

ddtrace 0.678 ms (0.29%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-05-05 18:22:08

Comparing candidate commit 0901e54 in PR branch rachel.yang/extract-http with baseline commit 601c0bd in branch main.

Found 0 performance improvements and 3 performance regressions! Performance is the same for 504 metrics, 5 unstable metrics.

scenario:iast_aspects-format_map_aspect

• 🟥 execution_time [+432.857ns; +505.721ns] or [+13.144%; +15.356%]

scenario:iast_aspects-ospathdirname_aspect

• 🟥 execution_time [+759.598ns; +917.429ns] or [+16.736%; +20.213%]

scenario:telemetryaddmetric-1-distribution-metric-1-times

• 🟥 execution_time [+237.149ns; +297.312ns] or [+7.830%; +9.817%]

[mabdinur]

typing is failing: https://gitlab.ddbuild.io/DataDog/apm-reliability/dd-trace-py/-/jobs/924198441. This points to a bug in the injection/extraction logic. We should make sure these methods never return None.