Compress SafeSocketHandle.Unix booleans (#112417)

Reduces the logical size of `SafeSocketHandle` by 6-7 bytes on Unix, crossing a treshold that lowers the number of words consumed by the type by 1 on 64bit

Author: antonfirsov

src/libraries/System.Net.Sockets/src/System/Net/Sockets/SafeSocketHandle.Unix.cs

@@ -14,17 +14,70 @@ public partial class SafeSocketHandle
     {
         private int _receiveTimeout = -1;
         private int _sendTimeout = -1;
-        private bool _nonBlocking;
         private SocketAsyncContext? _asyncContext;
 
-        internal bool LastConnectFailed { get; set; }
-        internal bool DualMode { get; set; }
-        internal bool ExposedHandleOrUntrackedConfiguration { get; private set; }
-        internal bool PreferInlineCompletions { get; set; } = SocketAsyncEngine.InlineSocketCompletionsEnabled;
-        internal bool IsSocket { get; set; } = true; // (ab)use Socket class for performing async I/O on non-socket fds.
+        [Flags]
+        private enum Flags : byte
+        {
+            NonBlocking = 1,
+            LastConnectFailed = 2,
+            DualMode = 4,
+            ExposedHandleOrUntrackedConfiguration = 8,
+            PreferInlineCompletions = 16,
+            IsSocket = 32,
+            IsDisconnected = 64,
 #if SYSTEM_NET_SOCKETS_APPLE_PLATFROM
-        internal bool TfoEnabled { get; set; }
+            TfoEnabled = 128
 #endif
+        }
+
+        private Flags _flags = Flags.IsSocket | (SocketAsyncEngine.InlineSocketCompletionsEnabled ? Flags.PreferInlineCompletions : 0);
+
+        private void SetFlag(Flags flag, bool value)
+        {
+            if (value) _flags |= flag;
+            else _flags &= ~flag;
+        }
+
+        internal bool LastConnectFailed
+        {
+            get => (_flags & Flags.LastConnectFailed) != 0;
+            set => SetFlag(Flags.LastConnectFailed, value);
+        }
+
+        internal bool DualMode
+        {
+            get => (_flags & Flags.DualMode) != 0;
+            set => SetFlag(Flags.DualMode, value);
+        }
+
+        internal bool ExposedHandleOrUntrackedConfiguration
+        {
+            get => (_flags & Flags.ExposedHandleOrUntrackedConfiguration) != 0;
+            private set => SetFlag(Flags.ExposedHandleOrUntrackedConfiguration, value);
+        }
+
+        internal bool PreferInlineCompletions
+        {
+            get => (_flags & Flags.PreferInlineCompletions) != 0;
+            set => SetFlag(Flags.PreferInlineCompletions, value);
+        }
+
+        // (ab)use Socket class for performing async I/O on non-socket fds.
+        internal bool IsSocket
+        {
+            get => (_flags & Flags.IsSocket) != 0;
+            set => SetFlag(Flags.IsSocket, value);
+        }
+
+#if SYSTEM_NET_SOCKETS_APPLE_PLATFROM
+        internal bool TfoEnabled
+        {
+            get => (_flags & Flags.TfoEnabled) != 0;
+            set => SetFlag(Flags.TfoEnabled, value);
+        }
+#endif
+
         internal void RegisterConnectResult(SocketError error)
         {
             switch (error)
@@ -67,11 +120,11 @@ internal bool IsNonBlocking
         {
             get
             {
-                return _nonBlocking;
+                return (_flags & Flags.NonBlocking) != 0;
             }
             set
             {
-                _nonBlocking = value;
+                SetFlag(Flags.NonBlocking, value);
 
                 // If transitioning from blocking to non-blocking, we need to set the native socket to non-blocking mode.
                 // If transitioning from non-blocking to blocking, we keep the native socket in non-blocking mode, and emulate
@@ -112,12 +165,9 @@ internal int SendTimeout
             }
         }
 
-        internal bool IsDisconnected { get; private set; }
+        internal bool IsDisconnected => (_flags & Flags.IsDisconnected) != 0;
 
-        internal void SetToDisconnected()
-        {
-            IsDisconnected = true;
-        }
+        internal void SetToDisconnected() => _flags |= Flags.IsDisconnected;
 
         /// <returns>Returns whether operations were canceled.</returns>
         private bool OnHandleClose()