feat(profiling): add experimental outside-in stack sampling method (stack v2)

[sanchda]

This allows users to optionally use a new stack sampling technique. Briefly,

• Avoids issues in Python 3.11 and later where the C struct backing Python frame objects may contain invalid pointers (causing segfaults within standard API calls)
• Addresses a bias in the "normal" stack sampler where we had a tendency to sample threads only at the points where they transitioned off-GIL
• Hopefully removes some serialization overhead, although in the first few versions the overall consumption of this technique may be higher.

There are a few tests around the new code, those will be added to CI in a later update.

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

[github-actions]

The backport to 2.7 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-2.7 2.7
# Navigate to the new working tree
cd .worktrees/backport-2.7
# Create a new branch
git switch --create backport-8471-to-2.7
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 33d0af1c205f512858179d13306caf2dea0c414d
# Push it to GitHub
git push --set-upstream origin backport-8471-to-2.7
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.7

Then, create a pull request where the base branch is 2.7 and the compare/head branch is backport-8471-to-2.7.

[github-actions]

The backport to 2.7 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-2.7 2.7
# Navigate to the new working tree
cd .worktrees/backport-2.7
# Create a new branch
git switch --create backport-8471-to-2.7
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 33d0af1c205f512858179d13306caf2dea0c414d
# Push it to GitHub
git push --set-upstream origin backport-8471-to-2.7
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.7

Then, create a pull request where the base branch is 2.7 and the compare/head branch is backport-8471-to-2.7.