Add support for SO_ERROR

[CvvT]

This PR adds support for SO_ERROR option (not complete) and improves TCP connection error reporting.

smoltcp does not report errors when IP lookup fails; it silently discards packets. Thus, we can only return ETIMEDOUT instead of ENETUNREACHED.

Previously timeout in TCP is treated as `ECONNREFUSED'. We can distinguish it by checking the elapsed time.

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

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--- failure copy_impl_added: type now implements Copy ---

Description:
A public type now implements Copy, causing non-move closures to capture it by reference instead of moving it.
        ref: https://github.com/rust-lang/rust/issues/100905
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/copy_impl_added.ron

Failed in:
  litebox::net::local_ports::LocalPortAllocationError in /home/runner/work/litebox/litebox/litebox/src/net/local_ports.rs:134
  litebox::net::errors::ConnectError in /home/runner/work/litebox/litebox/litebox/src/net/errors.rs:39

--- failure enum_variant_added: enum variant added on exhaustive enum ---

Description:
A publicly-visible enum without #[non_exhaustive] has a new variant.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#enum-variant-new
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.47.0/src/lints/enum_variant_added.ron

Failed in:
  variant SocketOption:ERROR in /home/runner/work/litebox/litebox/litebox_common_linux/src/lib.rs:701

[CvvT]

On my local env, I can run curl but it failed on CI (see https://github.com/microsoft/litebox/actions/runs/23078368851/job/67042868399). Will fix it in a separate PR.

[wdcui]

Thank you for the fix!