[ffx] Only compare TargetAddr on ip and port

This patch implements custom `PartialEq`, `Eq`, `PartialOrd`, `Ord`, and
`Hash` that only compare `ip` and `port`, and ignores  ipv6 `flowinfo`
and `scope_id` fields.

The latest rust nightly has [fixed] a longstanding bug where the
`PartialEq` implementation for `std::net::SocketAddr6` did not compare
the `flowinfo` and `scope_id` fields. This has been fixed, but it broke
ffx, which depended on this to deduplicate addresses that had the same
ip and port, but different scopes.

[fixed]: rust-lang/rust#116714

Change-Id: I64536942fe3ad44c509ffa10bd8e637d2a92ea2c
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/942191
Reviewed-by: Steven Grady <slgrady@google.com>
Fuchsia-Auto-Submit: Erick Tryzelaar <etryzelaar@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>

src/developer/ffx/lib/addr/src/target_addr.rs

@@ -12,14 +12,31 @@ use std::{
     str::FromStr,
 };
 
-#[derive(Hash, Clone, Debug, Copy, Eq, PartialEq)]
+#[derive(Clone, Debug, Copy)]
 pub struct TargetAddr(SocketAddr);
 
+// Only compare `TargetAddr` by ip and port, since we want to deduplicate targets if they are
+// addressable over multiple IPv6 interfaces.
+impl std::hash::Hash for TargetAddr {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: std::hash::Hasher,
+    {
+        (self.0.ip(), self.0.port()).hash(state)
+    }
+}
+
+impl PartialEq for TargetAddr {
+    fn eq(&self, other: &Self) -> bool {
+        self.0.ip() == other.0.ip() && self.0.port() == other.0.port()
+    }
+}
+
+impl Eq for TargetAddr {}
+
 impl Ord for TargetAddr {
     fn cmp(&self, other: &Self) -> Ordering {
-        let this_socket = SocketAddr::from(self);
-        let other_socket = SocketAddr::from(other);
-        this_socket.cmp(&other_socket)
+        self.0.ip().cmp(&other.0.ip()).then(self.0.port().cmp(&other.0.port()))
     }
 }