chore(deps): replace netlink-* crates with procfs

[pront]

Summary

Replace netlink socket-based implementation with direct /proc filesystem reads using the procfs crate.

procfs advantages:

• Actively maintained
• Simple, synchronous API - reads /proc/net/tcp and /proc/net/tcp6 directly
• Provides identical data: TcpNetEntry includes state, tx_queue, rx_queue
• Well-tested, widely used in production Rust systems tooling
• Minimal dependencies compared to netlink stack

Implementation changes:

• Removed 4 dependencies: netlink-packet-utils, netlink-packet-sock-diag, netlink-packet-core, netlink-sys
• Added 1 dependency: procfs (with default-features = false for minimal footprint)
• Simplified tcp.rs (~50% code reduction)
• Removed complex async netlink socket handling, message serialization, and manual parsing
• Maintained identical public API - all metric names unchanged, thus not a user facing change

Vector configuration

TODO needs more testing, still a draft

How did you test this PR?

TODO needs more testing, still a draft

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Closes: replace netlink-* crates with procfs #24768

Notes

• Please read our Vector contributor resources.
• Do not hesitate to use @vectordotdev/vector to reach out to us regarding this PR.
• Some CI checks run only after we manually approve them.
  • We recommend adding a pre-push hook, please see this template.
  • Alternatively, we recommend running the following locally before pushing to the remote branch:
    • make fmt
    • make check-clippy (if there are failures it's possible some of them can be fixed with make clippy-fix)
    • make test
• After a review is requested, please avoid force pushes to help us review incrementally.
  • Feel free to push as many commits as you want. They will be squashed into one before merging.
  • For example, you can run git merge origin master and git push.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run make build-licenses to regenerate the license inventory and commit the changes (if any). More details here.

[thomasqueirozb]

Nice!