fix(gapic-generator): restrict package discovery to gapic* namespace

[ohmayr]

Summary

Previously, setup.py called setuptools.find_namespace_packages(exclude=["docs", "tests"]) without wildcard glob patterns.
When CI (run_single_test.sh) or local test runners created temporary virtual environments (such as .venv-profiler or .nox), setuptools mistook those hidden directories for library packages and attempted to package their contents, causing pip install -e . and CI profiling jobs to fail or take too long.

Fix

This PR updates exclude in setup.py to use wildcard glob patterns:

packages=setuptools.find_namespace_packages(
    exclude=["docs*", "tests*", "testing*", ".*", "bazel*", "rules_python_gapic*"]
),

[gemini-code-assist]

Code Review

This pull request updates the package discovery in setup.py to use an explicit inclusion pattern (gapic*) instead of excluding specific directories. The reviewer recommends refining this pattern to ["gapic", "gapic.*"] to prevent accidentally matching unrelated directories or virtual environments starting with gapic.

[hebaalazzeh]

LGTM