Include VertexAI cluster environment for Fabric

[miguelalba96]

VertexAI cluster environment for Fabric

It includes a subclass that picks the proper CLUSTER_SPEC from a VertexAI custom training job and populate the respective environment variables necessary for DDP

from lightning.fabric.plugins.environments.vertexai import VertexAIEnvironment 

Dependencies: os, json

Before submitting

• Was this discussed/agreed via a GitHub issue? (not for typos and docs)
• [x ] Did you read the contributor guideline, Pull Request section?
• [x ] Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)

I added documentation on the docstring, I am not entirely sure where to add more docs

• Did you write any new necessary tests? (not for typos and docs)

• [ x] Did you verify new and existing tests pass locally with your changes?

I tested the code running it in Vertex AI pipelines as a custom training job, to asses the efficacy of the change you can check the documentation

I tested the custom job using

google_cloud_pipeline_components.v1.custom_job.create_custom_training_job_from_component

from the official Google's documentation:

• https://cloud.google.com/vertex-ai/docs/pipelines/customjob-component#create_custom_training_job_from_component_function

• https://cloud.google.com/vertex-ai/docs/pipelines/request-gcp-machine-resources

• Did you list all the breaking changes introduced by this pull request?

There are no substantial changes in the source code more than adding the environment in some imports

• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

yes

PR review

Anyone in the community is welcome to review the PR.
Before you start reviewing, make sure you have read the review guidelines. In short, see the following bullet-list:

Reviewer checklist

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

---

📚 Documentation preview 📚: https://pytorch-lightning--19911.org.readthedocs.build/en/19911/

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. If you need further help see our docs: https://lightning.ai/docs/pytorch/latest/generated/CONTRIBUTING.html#pull-request or ask the assistance of a core contributor here or on Discord. Thank you for your contributions.