Use core::net::Ip{Addr, V4Addr, V6Addr}

Re-export the types from the standard library instead of duplicating
their code. The types have been stable since Rust 1.6 and this crate has
a MSRV of 1.60.

Instead of re-exporting the equivalent types from core::net at the crate
root, this change simply removes the names. This is semver-incompatible,
but re-exporting types is also incompatible since a trait implementation
in a consuming crate for, e.g., core::net::IpAddr and pki_types::IpAddr
would now conflict.

src/lib.rs

@@ -94,9 +94,7 @@ mod server_name;
 #[cfg(feature = "alloc")]
 pub mod pem;
 
-pub use server_name::{
-    AddrParseError, DnsName, InvalidDnsNameError, IpAddr, Ipv4Addr, Ipv6Addr, ServerName,
-};
+pub use server_name::{DnsName, InvalidDnsNameError, ServerName};
 
 /// A DER-encoded X.509 private key, in one of several formats
 ///