Rollup merge of #89729 - jkugelman:must-use-core-std-constructors, r=joshtriplett

Add #[must_use] to core and std constructors

Parent issue: #89692

r? ``@joshtriplett``

library/std/src/net/addr.rs

@@ -131,6 +131,7 @@ impl SocketAddr {
     /// assert_eq!(socket.port(), 8080);
     /// ```
     #[stable(feature = "ip_addr", since = "1.7.0")]
+    #[must_use]
     pub fn new(ip: IpAddr, port: u16) -> SocketAddr {
         match ip {
             IpAddr::V4(a) => SocketAddr::V4(SocketAddrV4::new(a, port)),
@@ -272,6 +273,7 @@ impl SocketAddrV4 {
     /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     pub fn new(ip: Ipv4Addr, port: u16) -> SocketAddrV4 {
         SocketAddrV4 {
             inner: c::sockaddr_in {
@@ -368,6 +370,7 @@ impl SocketAddrV6 {
     /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     pub fn new(ip: Ipv6Addr, port: u16, flowinfo: u32, scope_id: u32) -> SocketAddrV6 {
         SocketAddrV6 {
             inner: c::sockaddr_in6 {

library/std/src/net/ip.rs

@@ -442,6 +442,7 @@ impl Ipv4Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv4", since = "1.32.0")]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     #[inline]
     pub const fn new(a: u8, b: u8, c: u8, d: u8) -> Ipv4Addr {
         // `s_addr` is stored as BE on all machine and the array is in BE order.
@@ -1192,6 +1193,7 @@ impl Ipv6Addr {
     /// ```
     #[rustc_const_stable(feature = "const_ipv6", since = "1.32.0")]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[must_use]
     #[inline]
     pub const fn new(a: u16, b: u16, c: u16, d: u16, e: u16, f: u16, g: u16, h: u16) -> Ipv6Addr {
         let addr16 = [