ci: add NFS validation and improve network drive robustness

[KGFCH2]

@Rakshat28
Addresses #35.

Summary

This PR improves the reliability of bdstorage on network-attached storage environments such as SMB and NFS by hardening low-level system call handling and introducing automated network filesystem testing.

Key Changes

FIEMAP Fallback Handling

• Refactored sparse hashing logic to gracefully handle FIEMAP ioctl failures.
• Ensures that when network filesystems do not support or forward these ioctls, the engine safely falls back to standard block reads instead of failing.

Graceful Linking Failure

• Improved deduplication error handling for remote filesystems.
• Verified that unsupported reflink operations surface clear and actionable "reflink not supported" messages when operating over SMB/NFS protocols that lack remote block cloning support.

Automated NFS Testing

• Added a dedicated CI job that provisions a local NFS environment.
• Validates that the engine’s speed-optimized deduplication pipeline behaves correctly under:
  • Higher filesystem latency
  • Reduced ioctl support
  • Network-mounted filesystem constraints

Result

These improvements make bdstorage significantly safer and more reliable for users managing large archives, media libraries, or backup datasets hosted on home or enterprise NAS systems.

[Rakshat28]

Work on the failing CI tests (across all PRs submitted by you) @KGFCH2

[KGFCH2]

Yeah I have worked on those and tested successfully.....
You can review and merge the PRs from @KGFCH2 .....
Thank you in advance....

[Rakshat28]

PR still not passing tests.