fix(datasets): make GBQTableDataset serializable

[deepyaman]

Description

Resolve https://kedro.hall.community/using-pandas-with-bigquery-and-parallel-runners-hTdF7LG3995h#a921cd9d-aa25-4752-9307-1862590a833d by delaying bigquery.Client() creation, as done in similar datasets.

Development notes

Also, as it stands now, the GBQQueryDataset doesn't need a bigquery.Client()? I think it would make sense to potentially implement GBQQueryDataset.exists() (if not query_or_table._is_query(), checked with something like https://github.com/googleapis/python-bigquery-pandas/blob/78aa01e3f039500c9fabbcdd8d8dcfa3e5c42b73/pandas_gbq/gbq.py#L71), but I haven't done that in this PR. (You'd need to figure out what to do if it isn't a table; would you return True but raise a warning?)

Checklist

• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the relevant RELEASE.md file
• Added tests to cover my changes
• Received approvals from at least half of the TSC (required for adding a new, non-experimental dataset)

[deepyaman]

Relevant tests are passing; just need to go through the rigamarole of rerunning flaky tests pass before merging.

[ankatiyar]

LGTM

[DimedS]

Thanks, @deepyaman ! LGTM