feat(langchain): [MLOB-1949] add langchain tests for vertexai and gemini integrations

[ncybul]

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:

.riot/requirements/105966d.txt                                          @DataDog/apm-python
.riot/requirements/12ccede.txt                                          @DataDog/apm-python
.riot/requirements/18b5d98.txt                                          @DataDog/apm-python
.riot/requirements/1bee666.txt                                          @DataDog/apm-python
.riot/requirements/34840a5.txt                                          @DataDog/apm-python
.riot/requirements/55b8536.txt                                          @DataDog/apm-python
.riot/requirements/57942b8.txt                                          @DataDog/apm-python
.riot/requirements/6820ef2.txt                                          @DataDog/apm-python
.riot/requirements/ab2f587.txt                                          @DataDog/apm-python
.riot/requirements/b5e3b2c.txt                                          @DataDog/apm-python
releasenotes/notes/feat-llmobs-vertexai-f58488859472c7b5.yaml           @DataDog/apm-python
tests/contrib/vertexai/test_vertexai_llmobs.py                          @DataDog/ml-observability
ddtrace/contrib/internal/google_generativeai/_utils.py                  @DataDog/ml-observability
ddtrace/contrib/internal/vertexai/_utils.py                             @DataDog/ml-observability
ddtrace/contrib/internal/vertexai/patch.py                              @DataDog/ml-observability
ddtrace/llmobs/_constants.py                                            @DataDog/ml-observability
ddtrace/llmobs/_integrations/bedrock.py                                 @DataDog/ml-observability
ddtrace/llmobs/_integrations/gemini.py                                  @DataDog/ml-observability
ddtrace/llmobs/_integrations/langchain.py                               @DataDog/ml-observability
ddtrace/llmobs/_integrations/utils.py                                   @DataDog/ml-observability
ddtrace/llmobs/_integrations/vertexai.py                                @DataDog/ml-observability
ddtrace/llmobs/_llmobs.py                                               @DataDog/ml-observability
ddtrace/llmobs/_utils.py                                                @DataDog/ml-observability
riotfile.py                                                             @DataDog/apm-python
tests/contrib/langchain/conftest.py                                     @DataDog/ml-observability
tests/contrib/langchain/test_langchain_llmobs.py                        @DataDog/ml-observability
tests/contrib/langchain/utils.py                                        @DataDog/ml-observability
tests/contrib/vertexai/conftest.py                                      @DataDog/ml-observability
.riot/requirements/102c18b.txt                                          @DataDog/apm-python
.riot/requirements/107d415.txt                                          @DataDog/apm-python
.riot/requirements/10e47e7.txt                                          @DataDog/apm-python
.riot/requirements/1265037.txt                                          @DataDog/apm-python
.riot/requirements/12f0b6a.txt                                          @DataDog/apm-python
.riot/requirements/13647e5.txt                                          @DataDog/apm-python
.riot/requirements/16c0f93.txt                                          @DataDog/apm-python
.riot/requirements/1882d8e.txt                                          @DataDog/apm-python
.riot/requirements/1b0d9c1.txt                                          @DataDog/apm-python
.riot/requirements/1ccf29f.txt                                          @DataDog/apm-python
.riot/requirements/1ddcc7b.txt                                          @DataDog/apm-python
.riot/requirements/9a816b6.txt                                          @DataDog/apm-python
.riot/requirements/bf4cae6.txt                                          @DataDog/apm-python
.riot/requirements/fdc4d1d.txt                                          @DataDog/apm-python

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-11-27 22:01:27

Comparing candidate commit ee6a63a in PR branch nicole-cybul/add-langchain-tests with baseline commit defea4e in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 388 metrics, 2 unstable metrics.