Add socks support (#7503)

## Summary

This adds about 50 KB to the binary:

```
❯ du ./target/release/socks
44736	./target/release/socks

❯ du ./target/release/uv
44632	./target/release/uv
```

So need some input on whether it's worth supporting.

Closes #7484.

Author: charliermarsh

Cargo.lock

@@ -122,7 +122,7 @@ quote = { version = "1.0.37" }
 rayon = { version = "1.10.0" }
 reflink-copy = { version = "0.1.19" }
 regex = { version = "1.10.6" }
-reqwest = { version = "0.12.7", default-features = false, features = ["json", "gzip", "stream", "rustls-tls", "rustls-tls-native-roots"] }
+reqwest = { version = "0.12.7", default-features = false, features = ["json", "gzip", "stream", "rustls-tls", "rustls-tls-native-roots", "socks"] }
 reqwest-middleware = { git = "https://github.com/astral-sh/reqwest-middleware", rev = "5e3eaf254b5bd481c75d2710eed055f95b756913" }
 reqwest-retry = { git = "https://github.com/astral-sh/reqwest-middleware", rev = "5e3eaf254b5bd481c75d2710eed055f95b756913" }
 rkyv = { version = "0.7.45", features = ["strict", "validation"] }