feat(llmobs): submit spans for streamed calls

[sabrenner]

What does this PR do?

Builds off of #10672, extending support for llm.stream, chat_model.stream, and chain.stream to LLM Observability. This PR tags those spans appropriately for LLM Observability, and marks them to submit to LLM Observability.

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:

releasenotes/notes/llmobs-langchain-streamed-calls-23a13029ac5d8907.yaml  @DataDog/apm-python
ddtrace/contrib/internal/langchain/patch.py                             @DataDog/ml-observability
ddtrace/contrib/internal/langchain/utils.py                             @DataDog/ml-observability
ddtrace/llmobs/_integrations/langchain.py                               @DataDog/ml-observability
tests/contrib/langchain/test_langchain_llmobs.py                        @DataDog/ml-observability
tests/snapshots/tests.contrib.langchain.test_langchain_community.test_streamed_chain.json  @DataDog/apm-python
tests/snapshots/tests.contrib.langchain.test_langchain_community.test_streamed_chat.json  @DataDog/apm-python
tests/snapshots/tests.contrib.langchain.test_langchain_community.test_streamed_json_output_parser.json  @DataDog/apm-python
tests/snapshots/tests.contrib.langchain.test_langchain_community.test_streamed_llm.json  @DataDog/apm-python

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: sabrenner/langchain-streamed-responses-llmobs
Commit report: b2eef10
Test service: dd-trace-py

✅ 0 Failed, 1196 Passed, 0 Skipped, 30m 23.23s Total duration (6m 25.45s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-10-02 20:31:35

Comparing candidate commit b2eef10 in PR branch sabrenner/langchain-streamed-responses-llmobs with baseline commit 7e8eb0b in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 371 metrics, 53 unstable metrics.