1. Fix "Open Editor" button not launching Editor on Mac.

2. Update LaunchAssetProcessor() paths on Mac.
3. LaunchAssetProcessor() uses ProcessWatcher wrappers.
4. SDK Launcher registers the engine when launching.

Signed-off-by: amzn-sj <srikkant@amazon.com>

Code/Tools/ProjectManager/Platform/Linux/ProjectUtils_linux.cpp

@@ -94,5 +94,10 @@ namespace O3DE::ProjectManager
                 QProcessEnvironment::systemEnvironment(),
                 QObject::tr("Running get_python script..."));
         }
+
+        AZ::IO::FixedMaxPath GetEditorDirectory()
+        {
+            return AZ::Utils::GetExecutableDirectory();
+        }
     } // namespace ProjectUtils
 } // namespace O3DE::ProjectManager