fix(lib-injection): fix incorrect telemetry data payload format

[brettlangdon]

We aggregate all telemetry data and then send only once, however we were sometimes aggregating payloads and other times aggregating individual metric events.

This PR fixes the inconsistency by only aggregating the metric events, and sending one single payload at the end.

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:

releasenotes/notes/fix-ssi-telemetry-events-a0a01ad0b6ef63b5.yaml       @DataDog/apm-python
lib-injection/sources/sitecustomize.py                                  @DataDog/apm-core-python

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: brettlangdon/fix.ssi.telemetry.payloads
Commit report: 99a2505
Test service: dd-trace-py

✅ 0 Failed, 130 Passed, 1468 Skipped, 4m 29.37s Total duration (35m 28.19s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-16 20:15:47

Comparing candidate commit 1c08bfa in PR branch brettlangdon/fix.ssi.telemetry.payloads with baseline commit 0275a5e in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 208 metrics, 2 unstable metrics.

[erikayasuda]

Just one release note nit

[github-actions]

The backport to 2.18 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.18 2.18
# Navigate to the new working tree
cd .worktrees/backport-2.18
# Create a new branch
git switch --create backport-11950-to-2.18
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7f2e40ce5bcf7f3c084139bb02c06fd4299db75e
# Push it to GitHub
git push --set-upstream origin backport-11950-to-2.18
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.18

Then, create a pull request where the base branch is 2.18 and the compare/head branch is backport-11950-to-2.18.