* chore: remove old GAPIC code for v1 API

* Regenerate the v1 API with microgenerator

* Adjust dependencies and classifiers in setup.py

* Fix types aggregation in types.py

* Adjust import paths

* Fix and adjust unit tests

* Fix and adjust system tests

* Adjust unit test coverage threshold

Not all paths are covered, not even in the generated code, thus
the adjustment is necessary.

* Fix docs build

* Adjust quickstart sample

* Adjust sample in client docstring

* Remove beta API code and docs

* Simplify synth replacement rules and regenerate

Rules conditionally matching versions other than v1 are not needed
anymore.

* Consolidate imports in google.cloud.bigquery.storage

* Use gogole.cloud.bigquery.storage as import path

* Hide async client from most import paths

* Use GAPIC client mock in ReadRowsStream tests

* Remove redundant installations in nox sessions

* Include manual classes in reference docs

* Add UPGRADING guide

* Add minor CHANGELOG improvements

* chore: release v2.0.0

* Update CHANGELOG.md

* Replace PROJECT_ID with GOOGLE_CLOUD_PROJECT in test

* Do not add google.cloud.bigquery as namespace package

* Install the library as non-editable in tests

This avoids import errors from google.cloud.bigquery.* namespace.

* Fix test coverage plugin paths

* Regenerate code with different namespace (bigquery_storage)

* Adjust import paths to bigquery_storage namespace

* Adjust docs to bigquery_storage namespace

* Adjust UPGRADING guide to changed namespace

Co-authored-by: Tim Swast <swast@google.com>