chore(lib-injection): post-injection telemetry

[emmettbutler]

This change adds information to the "app started" telemetry event that indicates some of the specifics about the library-injection code path:

• whether it was hit at all
• whether it successfully performed library injection
• whether the user specified that injection should be "forced" past guardrails

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: emmett.butler/more-injection-telemetry
Commit report: b70e80e
Test service: dd-trace-py

✅ 0 Failed, 120969 Passed, 57288 Skipped, 4h 16m 37.77s Total duration (3h 30m 53.33s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-06-11 16:38:14

Comparing candidate commit 2389ac4 in PR branch emmett.butler/more-injection-telemetry with baseline commit c5daad9 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 219 metrics, 11 unstable metrics.

[github-actions]

The backport to 2.10 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-2.10 2.10
# Navigate to the new working tree
cd .worktrees/backport-2.10
# Create a new branch
git switch --create backport-9489-to-2.10
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 2e237a7ee8e23ff1d96285e6e70c364a103e098a
# Push it to GitHub
git push --set-upstream origin backport-9489-to-2.10
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.10

Then, create a pull request where the base branch is 2.10 and the compare/head branch is backport-9489-to-2.10.