Move the inline filesystem skip logic from pollVMsAndContainersEfficient
into a reusable ShouldSkipFilesystem function. This consolidates filtering
for virtual filesystems (tmpfs, cgroup, etc.), network mounts (nfs, cifs,
fuse), and special mountpoints (/dev, /proc, /snap, etc.) into one tested
location.
Reduces cyclomatic complexity of pollVMsAndContainersEfficient and adds
28 test cases covering virtual fs types, network mounts, special mounts,
Windows paths, and edge cases.