fix(test): make //distro:packaging_test work with Bazel 9

[rdesgroppes]

Bazel 9 flipped --incompatible_strict_action_env to true by default (bazelbuild/bazel#27670), which means tests no longer inherit PATH from the host environment. This breaks subprocess calls that rely on PATH lookup:

==================== Test output for //distro:packaging_test:
E.
======================================================================
ERROR: testBuild (__main__.PackagingTest.testBuild)
----------------------------------------------------------------------
Traceback (most recent call last):
[...]
    build_result = subprocess.check_output(['bazel', 'build', '--enable_workspace', ':dummy_tar'])
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[...]
FileNotFoundError: [Errno 2] No such file or directory: 'bazel'

This change therefore adds env_inherit = ["PATH"] to that very test, which matches the behavior of earlier Bazel versions and is consistent with the presence of a "noci" tag.

Additionally, Bazel 9 removed WORKSPACE support entirely (bazelbuild/bazel#26131), requiring bzlmod with MODULE.bazel:

==================== Test output for //distro:packaging_test:
[...]
WARNING: --enable_bzlmod is set, but no MODULE.bazel file was found at the workspace root. Bazel will create an empty MODULE.bazel file. Please consider migrating your external dependencies from WORKSPACE to MODULE.bazel. For more details, please refer to https://github.com/bazelbuild/bazel/issues/18958.
[...]
ERROR: error loading package '': Unable to find package for @@[unknown repo 'not_named_rules_pkg' requested from @@]//pkg:tar.bzl: The repository '@@[unknown repo 'not_named_rules_pkg' requested from @@]' could not be resolved: No repository visible as '@not_named_rules_pkg' from main repository.
[...]
ERROR: Build did NOT complete successfully
E.
======================================================================
ERROR: testBuild (__main__.PackagingTest.testBuild)
----------------------------------------------------------------------
[...]
    build_result = subprocess.check_output(['bazel', 'build'] + bazel_flags + [':dummy_tar'])
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[...]
subprocess.CalledProcessError: Command '['bazel', 'build', '--enable_workspace', ':dummy_tar']' returned non-zero exit status 1.

The test now detects the Bazel version at runtime and generates the appropriate setup:

• Bazel 9+: MODULE.bazel, with bazel_dep and archive_override,
• earlier versions, as before: WORKSPACE, with http_archive and --enable_workspace flag.

For good measure, the change also addresses a leftover TODO by replacing the tar subprocess invocation with pure Python code (as otherwise done in the repo).