Implement pkg_install(symlink) also for pkg_zip

[adrianimboden]

I start to use hermetic python environment and saw #929.

It mostly works, but in my case I use pkg_zip instead of pkg_tar.

4eed546 implements raw_symlink/ support for pkg_tar.
This MR adds the same functionality for pkg_zip.

The exception when the feature is not implemented yet:

Exception: ('Unknown type for manifest entry:', ManifestEntry<{'type': 'raw_symlink', 'dest': 'system_impl.runfiles/_main/example/_impl_py_client_install.venv/bin/python3', 'src': 'bazel-out/k8-fastbuild/bin/example/_impl_py_client_install.venv/bin/python3', 'mode': '0555', 'user': None, 'group': None, 'uid': None, 'gid': None, 'origin': '@@//example:system_impl'}>)

[cgrindel]

LGTM. I will wait to let @aiuto review before merging.

[cgrindel]

@adrianimboden It looks like there may be some linting issues. Can you investigate?