chore: move version to gapic_version.py

[parthea]

This PR includes the following changes:

• Configure release-please to use a manifest file
• Clean up owlbot.py
• Clean up setup.py
• Move the hardcoded version out of setup.py and into gapic_version.py. Also, add a corresponding gapic_version.py files for the v1 and v1beta2 client.
• Configure release-please to update the version in gapic_version.py and autogenerated snippets json files.

(py39) partheniou@partheniou-vm-2:~/.repo/python-bigquery-storage$ python3
Python 3.9.13 (main, Nov 29 2022, 19:17:35) 
[GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import google.cloud.bigquery_storage
>>> import google.cloud.bigquery_storage_v1
>>> import google.cloud.bigquery_storage_v1beta2
>>> google.cloud.bigquery_storage.__version__
'2.16.2'
>>> google.cloud.bigquery_storage_v1.__version__
'2.16.2'
>>> google.cloud.bigquery_storage_v1beta2.__version__
'2.16.2'

[parthea]

Samples tests are failing with Request had invalid authentication credentials. Expected OAuth 2 access token, login cookie or other valid authentication credential. This issue was resolved