feat(llmobs): improve langchain llmobs span names

[lievan]

Change the span name for langchain auto-instrumented spans to be module + class

APM span name doesn't change -- just the name on the llmobs span event we send to evp

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: evan.li/langchain-naming
Commit report: 693fa12
Test service: dd-trace-py

✅ 0 Failed, 3010 Passed, 477 Skipped, 1h 12m 46.97s Total duration (9m 31.72s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-05-22 00:50:26

Comparing candidate commit 6eba915 in PR branch evan.li/langchain-naming with baseline commit 52b0c59 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 209 metrics, 9 unstable metrics.

[Yun-Kim]

This is a good workaround for now, let's write a ticket to solve this in a cleaner way in the future. Just one comment

[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-9333-to-2.9
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 8c2758ad21cbbf24ab5cc3db351cb2b7cad0ff44
# Push it to GitHub
git push --set-upstream origin backport-9333-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-9333-to-2.9.