chore: fix some warnings, cleanup

Dalamud.Injector/ExistingProcess.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Diagnostics;
+using System.Reflection;
+
+using Microsoft.Win32.SafeHandles;
+
+namespace Dalamud.Injector;
+
+/// <summary>
+/// Class representing an already held process handle.
+/// </summary>
+internal class ExistingProcess : Process
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ExistingProcess"/> class.
+    /// </summary>
+    /// <param name="handle">The existing held process handle.</param>
+    public ExistingProcess(IntPtr handle)
+    {
+        this.SetHandle(handle);
+    }
+
+    private void SetHandle(IntPtr handle)
+    {
+        var baseType = this.GetType().BaseType;
+        if (baseType == null)
+            return;
+
+        var setProcessHandleMethod = baseType.GetMethod(
+            "SetProcessHandle",
+            BindingFlags.NonPublic | BindingFlags.Instance);
+        setProcessHandleMethod?.Invoke(this, new object[] { new SafeProcessHandle(handle, true) });
+    }
+}