Add DatasetAlias to support dynamic Dataset Event Emission and Dataset Creation

[Lee-W]

Why this change?

related: #40039 which is inspired #34206

We want to allow DatasetEvent and Dataset to be created in a task dynamically.

e.g.,

@task(outlets=[DatasetAlias("my-task-outputs")])
def my_task(*, ds, outlet_events):
    outlet_events["my-task-outputs"].add(Dataset(f"s3://bucket/my-task/{ds}"))

What's change?

Introduced DatasetAlias which support the following syntax to create a Dataset and a DatasetEvent dynamically

@task(outlets=[DatasetAlias("my-task-outputs")])
def my_task_with_outlet_events(*, ds, outlet_events):
    outlet_events["my-task-outputs"].add(Dataset(f"s3://bucket/my-task/{ds}"))

@task(outlets=[DatasetAlias("my-task-outputs")])
def my_task_with_metadata(*, ds):
    s3_dataset = Dataset(f"s3://bucket/my-task/{ds}")
    yield Metadata(s3_dataset, extra={"k": "v"}, alias="my-task-outputs")

Note

This PR only supports part of the #40039. It does not yet support scheduling based on DatasetAlias (will create another PR for that)

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[Lee-W]

Finally get the CI green. Will continue work on adding unit tests and docs

[Lee-W]

Added test cases to cover the changes. Will work on the documentation next