* ci(python): run lint / unit tests / docs as GH actions

Source-Link: googleapis/synthtool@57be0cd
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:ed1f9983d5a935a89fe8085e8bb97d94e41015252c5b6c9771257cf8624367e6

* restore mypy check; update required checks

* set python version to 3.7 for mypy

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>

* chore(deps): update actions/setup-python action to v3

Source-Link: googleapis/synthtool@571ee2c
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:09af371bb7d8ebbaef620bfc76c0a3a42da96d75f4821409b54f3466d4ebbd3c

* fix name for mypy check

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Source-Link: googleapis/synthtool@ca87909
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:6162c384d685c5fe22521d3f37f6fc732bf99a085f6d47b677dbcae97fc21392

Source-Link: googleapis/synthtool@38e11ad
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:4e1991042fe54b991db9ca17c8fb386e61b22fe4d1472a568bf0fcac85dcf5d3

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

fix(deps): require google-auth 1.25.0

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>