Add @kubernetes decorator

[desertaxle]

This PR introduces a @kubernetes decorator that will bind a flow to run in a given work pool.

Here's what it looks like in action:

import asyncio

from prefect_kubernetes.experimental.decorators import kubernetes

from prefect import flow

# Thes are set on the work pool
UPLOAD_STEP = {
    "prefect_aws.experimental.bundles.upload": {
        "requires": "prefect-aws",
        "bucket": "test-bucket",
        "aws_credentials_block_name": "my-creds",
    }
}

EXECUTE_STEP = {
    "prefect_aws.experimental.bundles.execute": {
        "requires": "prefect-aws",
        "bucket": "test-bucket",
        "aws_credentials_block_name": "my-creds",
    }
}

# Results must be configured to retrieve the return value
@kubernetes(work_pool="olympic")
@flow(log_prints=True, result_storage="s3-bucket/results-bucket") 
def my_flow(name: str) -> str:
    print("Returning greeting...")
    return f"Hello, {name}!"


async def main():
    print(my_flow(name="John"))


if __name__ == "__main__":
    asyncio.run(main())

The goal of this decorator is to allow decorating flows and bind them to running in a Kubernetes cluster, but not require any code changes where the flow is called. This is achieved in this PR except for a few exceptions:

1. You must configure result storage on the flow or execution will fail when attempting to retrieve the return value for the flow.
2. The wait_for kwarg is unused right now.

Additional work will be necessary to address these limitations.

Related to #17218

[cicdw]

note from discussion: we probably want to consider adding a .submit method to the decorated flow object that returns this future directly when called and otherwise, when the new flow-object is called directly it automatically resolves the future as it does here.

[zzstoatzz]

looking trim!

[zzstoatzz]

lgtm!

[zzstoatzz]

it'd be nice to have a TypedDict here to Unpack someday, not sure how we'd manage that, but just throwing it out there

Suggested change

	work_pool: str, **job_variables: Any
	work_pool: str, **job_variables: Any

[desertaxle]

I could see a world where we can generate a decorator for a specific work pool that includes the job variables as named and type kwargs. We're probably a ways off from that though.

[cicdw]

love it