feat: make use of LZ4 in `to_arrow` / `to_dataframe`

[tswast]

googleapis/python-bigquery-storage#166 adds a compression option to Arrow streams. This can greatly speed-up some workloads.

Requires pyarrow >=1.0.0.

[tswast]

Note: since we don't want to bump the minimum google-cloud-bigquery-storage just yet, we should do a hasattr check or package version check.

[plamut]

BTW, this is currently blocked on the BQ Stroage release, we can't use the happy path just yet, except with a pre-release install. I can still create a draft PR, though.

[plamut]

Release done, not blocked anymore.