fix: add __init__.py to peer_service module

[gnufede]

Fixes an issue where importing ddtrace.internal.peer_service would fail raising an ImportError

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: gnufede/fix-peer_service-module
Commit report: 4fba432
Test service: dd-trace-py

✅ 0 Failed, 203 Passed, 732 Skipped, 7m 26.98s Total duration (32m 26.05s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-03-26 16:23:55

Comparing candidate commit 4fba432 in PR branch gnufede/fix-peer_service-module with baseline commit d8ebea7 in branch main.

Found 3 performance improvements and 3 performance regressions! Performance is the same for 161 metrics, 9 unstable metrics.

scenario:httppropagationextract-empty_headers

• 🟥 max_rss_usage [+717.828KB; +882.479KB] or [+3.420%; +4.205%]

scenario:httppropagationextract-full_t_id_datadog_headers

• 🟥 max_rss_usage [+708.928KB; +779.559KB] or [+3.354%; +3.688%]

scenario:httppropagationextract-wsgi_invalid_priority_header

• 🟥 max_rss_usage [+624.628KB; +802.009KB] or [+2.955%; +3.794%]

scenario:httppropagationextract-wsgi_invalid_span_id_header

• 🟩 max_rss_usage [-774.000KB; -569.897KB] or [-3.537%; -2.604%]

scenario:httppropagationextract-wsgi_medium_header_no_matches

• 🟩 max_rss_usage [-669.834KB; -532.751KB] or [-3.059%; -2.433%]

scenario:httppropagationextract-wsgi_valid_headers_basic

• 🟩 max_rss_usage [-998.464KB; -678.029KB] or [-4.559%; -3.096%]