ci(langgraph): fix flaky test

[sabrenner]

What does this PR do

Tests like test_fanning_graph_async would fail because it may be possible for the two children being called from a common node (ie node a calling nodes b and c) to execute in any order. Although this is probably only particular to async fanning tests, this PR changes the logic such that:

• for LLMObs tests, we find spans by name and assert LLMObs properties after. This might be tricky if we have duplicate span names (ie two LangGraph spans), but for now this isn't the case
• for APM tests, we assert that all span resource names appear an expected number of times. We can probably make these tests more robust with snapshots but this can be done in a later PR

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:

tests/contrib/langgraph/test_langgraph.py                               @DataDog/ml-observability
tests/contrib/langgraph/test_langgraph_llmobs.py                        @DataDog/ml-observability

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-22 15:27:15

Comparing candidate commit bff15d2 in PR branch sabrenner/flaky-langgraph with baseline commit cd6422a in branch main.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 393 metrics, 2 unstable metrics.

scenario:iast_aspects-ospathsplitext_aspect

• 🟥 execution_time [+259.921ns; +319.396ns] or [+7.246%; +8.904%]