chore: move version to gapic_version.py

[parthea]

fix(deps): require grpcio-status>=1.33.2
fix(deps): require google-api-core[grpc] >= 1.33.2

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
• Configure release-please to update the version in gapic_version.py and autogenerated snippets json files.
• Require grpcio-status >= 1.33.2 to match google-api-core https://github.com/googleapis/python-api-core/blob/main/setup.py#L39
• Require google-api-core[grpc] >= 1.33.2

partheniou@partheniou-vm-2:~/.repo/python-pubsub$ python3
Python 3.7.13 (default, Nov 10 2022, 15:01:44) 
[GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import google.pubsub
>>> import google.pubsub_v1
>>> google.pubsub.__version__
'2.13.11'
>>> google.pubsub_v1.__version__
'2.13.11'

[acocuzzo]

LGTM, thanks