proxy: replace net2 with socket2 #4891
Description
The proxy depends on the net2 crate, which has been deprecated and replaced by socket2. We should update our one or two uses:
linkerd/app/Cargo.toml
42:net2 = "0.2"
linkerd/app/integration/Cargo.toml
32:net2 = "0.2"
linkerd/app/integration/src/server.rs
205: let listener = net2::TcpBuilder::new_v4().expect("Tcp::new_v4");
linkerd/app/integration/src/controller.rs
337: let listener = net2::TcpBuilder::new_v4().expect("Tcp::new_v4");