BigQuery: Add user-agent info to Jupyter magics Client constructor(s).

[tswast]

In order to better prioritize jupyter features such as #8342 and #8143, it is important for Google to know how much these features are used to query BigQuery. This is done by populating the user-agent string with the corresponding "application name" and version information.

I propose we use the IPython version information in this string, as these magics are being used from an IPython kernel. Getting the IPython version string: https://stackoverflow.com/a/56265255/101923 Something like:

bigquery.Client(
    client_info=ClientInfo(
        user_agent="ipython-{}".format(IPython.__version__)
    )
)

[tswast]

Re-opening. I forgot to mention we create another client that'll need similar treatment. We can construct a BigQuery Storage API client, which is a gapic client, so needs the other ClientInfo class.

https://github.com/plamut/google-cloud-python/blob/7b6aecc10ed355b7b81ceb7bbe56000ebc0dd778/bigquery/google/cloud/bigquery/magics.py#L442

[tswast]

needs the other ClientInfo class.

Since the grpc stuff is an optional dependency, let's import it in the _make_bqstorage_client function.

[plamut]

Thanks for the update, I will look at that as well.