chore(llmobs): fix behavior for running multiple evaluators

[lievan]

There was unexpected behavior when turning on multiple evaluators where only the last evaluator in the evaluators list was being run multiple times for one span.

Fix it by replacing executor.map with just individual calls to executor.submit, which should do the same thing but it avoids the the unexpected behavior above

To reproduce: the added test case in this PR fails if we switch back to executor.map. See this CI run for the reproduced error

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:

ddtrace/llmobs/_evaluators/runner.py                                    @DataDog/ml-observability
tests/llmobs/_utils.py                                                  @DataDog/ml-observability
tests/llmobs/test_llmobs_evaluator_runner.py                            @DataDog/ml-observability

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: evan.li/test-multiple
Commit report: 2fc38af
Test service: dd-trace-py

✅ 0 Failed, 219 Passed, 1379 Skipped, 7m 8.35s Total duration (34m 47.25s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-17 16:21:00

Comparing candidate commit cad52ed in PR branch evan.li/test-multiple with baseline commit f67a358 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 362 metrics, 2 unstable metrics.