feat: convert Enpoint into SocketAddr

[sunhaosheng]

Motivation

smoltcp::wire::Endpoint already supports conversion from core::net::SocketAddr (and v4/v6 variants), but there is no reverse conversion back to SocketAddr.

In real integrations, this causes small but repeated friction when interacting with APIs or logging paths that use standard Rust socket address types:

• Rewriting the same manual conversion logic in multiple places
• Reduced ergonomics when bridging smoltcp types with core/std-based code
• Asymmetric conversion API (SocketAddr -> Endpoint exists, reverse does not)

Proposed Solution

A direct conversion from Endpoint to core::net::SocketAddr should be added. This makes conversion support symmetrical and removes boilerplate when interoperating with the Rust networking ecosystem.

API Design

impl From<Endpoint> for ::core::net::SocketAddr {
    fn from(x: Endpoint) -> ::core::net::SocketAddr {
        ::core::net::SocketAddr::new(x.addr.into(), x.port)
    }
}

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.27%. Comparing base (08bacc9) to head (2a8b2d6).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/wire/ip.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1124      +/-   ##
==========================================
- Coverage   81.28%   81.27%   -0.01%     
==========================================
  Files          81       81              
  Lines       24838    24841       +3     
==========================================
  Hits        20189    20189              
- Misses       4649     4652       +3     

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