Skip procfs symlinks in virtual proc_path resolution

[doanbaotrung]

To fix fstatfs returning the incorrect magic on open descriptors of procfs magic links and symlinks, exclude paths like /proc/self/exe, /proc/self/cwd, /proc/self/root, /proc/self/fd/N, and task-specific equivalents from resolving to a virtual proc_path stamp.

This prevents the guest fd table from recording these entries as part of the emulated procfs, letting fstatfs correctly query the filesystem information of their resolved host file targets.

Fix #142

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Summary by cubic

Fix statfs/fstatfs to report the correct filesystem type for /proc symlink targets and FDs by skipping virtual proc_path stamping and making statfs follow /proc symlinks (with a loop cap). Prevents mislabeling as procfs and fixes incorrect f_type. Fixes #142.

• Bug Fixes

  • Skip /proc symlink and magic-link paths in proc_path resolution (/proc/self/exe, /proc/self/cwd, /proc/self/root, /proc/self/fd/N, and task variants).
  • statfs on these paths now follows the link and reports the target host filesystem; statfs on /proc and real proc files returns PROC_SUPER_MAGIC.
  • fstatfs on FDs from these paths now reports the target host filesystem.

• Refactors

  • Removed proc_intercept_statfs; unified /proc statfs handling with a 40-step symlink-follow limit.
  • dirfd base path now returns ENOTDIR when a non-directory FD has a proc_path.

^{Written for commit d698f05. Summary will update on new commits.}

[doanbaotrung]

Hi @jserv

So sorray the last PR #207.
I fixed but forgot to push.
This is for the update base on comments.

[jserv]

Always enforce rules specified in https://cbea.ms/git-commit/ without leading tags such as fs:.

[jserv]

Thank @doanbaotrung for contributing!