chore: prepare for monorepo migration

[parthea]

This PR migrates to a standard owlbot.py file, instead of a customized one.

Here are the commands that I used to validate the change

• In a clone of googleapis/googleapis, run
  bazel build //google/iam/credentials/v1:iam-credentials-v1-py
bazel build //google/iam/v2:iam-v2-py
bazel build //google/iam/v2beta:iam-v2beta-py

• In this branch, run owlbot copy code and the owlbot post processor

docker run --rm --user $(id -u):$(id -g)   -v $(pwd):/repo   -v $HOME/git/googleapis/bazel-bin:/bazel-bin   gcr.io/cloud-devrel-public-resources/owlbot-cli:latest copy-bazel-bin   --source-dir /bazel-bin --dest /repo

docker run --user $(id -u):$(id -g) --rm -v $(pwd):/repo -w /repo gcr.io/cloud-devrel-public-resources/owlbot-python:latest

Background

The repository googleapis/python-iam contains code for 2 APIs google/iam/credentials and google/iam

The PR is removing custom logic in owlbot.py, and making the necessary changes in .Owlbot.yaml instead.

[suztomo]

Im Java iam and iamcredentials are different library. If this change is intentional, that's fine.

[parthea]

Acknowledged. iamcredentials was shipped first as google-cloud-iam instead of google-cloud-iamcredentials. I think this is what caused us to merge the 2 APIs. When google/iam v2/v2beta came along we decided to add them to the existing google-cloud-iam package. We don't have plans to split up iam and iamcredentials. Let's continue the discussion in googleapis/google-cloud-python#11572 which mentions consolidating iam APIs.