Increase Automated Test Coverage With Bigquery

[jdimatteo]

Is your feature request related to a problem? Please describe.

Historically there have been bugs fixed specific to BigQuery that ideally would have been caught by automated tests before a great expectations release, e.g. #1384 fixed #1391. There are some currently open bugs related to bigquery that (assuming they are valid bugs) ideally would have been caught by automated tests, e.g. #2959, #2978, and #3131.

Describe the solution you'd like

Increase test coverage of GreatExpectations with BigQuery, e.g. to match test coverage with Postgres and/or Snowflake.

Describe alternatives you've considered

As a work around, my private project using great expectations tests with bigquery and I run these tests before upgrading Great Expectations. This is not sustainable and prevents me from using the latest version of Great Expectations -- currently I'm stuck with Great Expectations version 0.12.7 and I need to upgrade (e.g. so I don't have to maintain a fork with patches to get the latest features).

Additional context
Briefly discussed at https://greatexpectationstalk.slack.com/archives/CV828B2UX/p1627419182062500 with @bhcastleton.