chore(Profiling): add infrastructure for supporting timeline, but timeline isn't supported yet

[sanchda]

Next week I'll finally add support for testing some of these new interface. Moreover, at the current time this stuff is pretty much only for internal testing, so I'll document when we're closer to going public.

The, uh, framing for this is kind of weird. I'm sorry about that.

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

[danielsn]

@emmettbutler This is a PR we are hoping to get into the 2.10RC

[danielsn]

Couple questions. LGTM

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: sanchda/add_timeline_ddup
Commit report: aecbeba
Test service: dd-trace-py

✅ 0 Failed, 561 Passed, 987 Skipped, 41m 40.48s Total duration (25m 12.75s time saved)

[github-actions]

The backport to 2.8 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-2.8 2.8
# Navigate to the new working tree
cd .worktrees/backport-2.8
# Create a new branch
git switch --create backport-9440-to-2.8
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 360b469bc3e4ce4c938eb02a62d83290c6581b90
# Push it to GitHub
git push --set-upstream origin backport-9440-to-2.8
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.8

Then, create a pull request where the base branch is 2.8 and the compare/head branch is backport-9440-to-2.8.

[github-actions]

The backport to 2.9 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-2.9 2.9
# Navigate to the new working tree
cd .worktrees/backport-2.9
# Create a new branch
git switch --create backport-9440-to-2.9
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 360b469bc3e4ce4c938eb02a62d83290c6581b90
# Push it to GitHub
git push --set-upstream origin backport-9440-to-2.9
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.9

Then, create a pull request where the base branch is 2.9 and the compare/head branch is backport-9440-to-2.9.