net: implement TCP accept and stabilize socket operations

[xuchang-vivo]

Summary

• Implement the TCP accept() path and accepted-socket setup.
• Preserve accepted socket ownership and peer endpoint information.
• Retain UDP ephemeral-port leases and use the correct socket type for connect port allocation.
• Add SO_REUSEADDR compatibility for the single-listener smoltcp configuration.
• Validate socket option identifiers, timeval layouts, lengths, and values.
• Use per-operation socket reply state and enforce configured blocking I/O timeouts.
• Preserve socket errors, including timeout and would-block conditions, across syscall and VFS boundaries.
• Keep socket shutdown and closed-socket state transitions consistent.

Relation to issue #456

This partially addresses #456 by removing the shared per-connection reply object and allowing independent socket operations to be queued. Shutdown-driven cancellation of an already blocked operation remains follow-up work.

Scope

This PR contains the kernel network changes currently on xc/add_more_caps_to_agent. It does not include the uncommitted ESP32-C3 board changes, BME280 changes, or application changes.

Testing

• Ran rustfmt --edition 2021 --check on the files changed by the final socket-state/options commit.
• Ran git diff --check on the same files.
• No board build was run.

[xuchang-vivo]

build_prs

[github-actions]

Job is started, see https://github.com/vivoblueos/kernel/actions/runs/32970859064.

[github-actions]

❌ Job failed. Failed jobs: build_and_check_boards (failure), see https://github.com/vivoblueos/kernel/actions/runs/32970859064.