gdb: More cleanup changes

- Move the message handler into its debugger class part,
- Move all message types into one file and collapse 3 of the ones with no data into a generic, stateless message with a single property being its type,
- Add an Fpscr helper property on IExecutionContext along with a comment about what Fpscr is (similar to the other registers in there)
- Moved the Rcmd helpers (such as GetRegisters, GetMinidump, etc) into a dedicated Debugger class part,
- Fixed the double-collection (ToArray being called twice) in GetThreadUids & GetThread in KProcess

src/Ryujinx.HLE/Debugger/Debugger.MessageHandler.cs

@@ -0,0 +1,58 @@
+using Ryujinx.Common.Logging;
+using System;
+using System.IO;
+
+namespace Ryujinx.HLE.Debugger
+{
+    public partial class Debugger
+    {
+        private void MessageHandlerMain()
+        {
+            while (!_shuttingDown)
+            {
+                try
+                {
+                    switch (_messages.Take())
+                    {
+                        case StatelessMessage { Type: MessageType.BreakIn }:
+                            Logger.Notice.Print(LogClass.GdbStub, "Break-in requested");
+                            _commands.Interrupt();
+                            break;
+
+                        case StatelessMessage { Type: MessageType.SendNack }:
+                            _writeStream.WriteByte((byte)'-');
+                            break;
+
+                        case StatelessMessage { Type: MessageType.Kill }:
+                            return;
+
+                        case CommandMessage { Command: { } cmd }:
+                            Logger.Debug?.Print(LogClass.GdbStub, $"Received Command: {cmd}");
+                            _writeStream.WriteByte((byte)'+');
+                            _commandProcessor.Process(cmd);
+                            break;
+
+                        case ThreadBreakMessage { Context: { } ctx }:
+                            DebugProcess.DebugStop();
+                            GThread = CThread = ctx.ThreadUid;
+                            _breakHandlerEvent.Set();
+                            _commandProcessor.Reply($"T05thread:{ctx.ThreadUid:x};");
+                            break;
+                    }
+                }
+                catch (IOException e)
+                {
+                    Logger.Error?.Print(LogClass.GdbStub, "Error while processing GDB messages", e);
+                }
+                catch (NullReferenceException e)
+                {
+                    Logger.Error?.Print(LogClass.GdbStub, "Error while processing GDB messages", e);
+                }
+                catch (ObjectDisposedException e)
+                {
+                    Logger.Error?.Print(LogClass.GdbStub, "Error while processing GDB messages", e);
+                }
+            }
+        }
+    }
+}