PythonProxyNotificationHandler::OnEventGenericHook acquires the Python GIL before executing (#3904)

- Protected python execution of OnEventGenericHook by trying to lock the GIL and show a descriptive error when it was not possible to lock.
- Improved mechanism to lock python mutex and GIL in PhytonSystemComponent. Acquiring/releasing GIL once per thread.
- Added unit test to verify errors are fired when trying to execute OnEventGenericHook from another thread (as it should not able to acquire the GIL).
- Improved python threading tests to actually using python buses.

Signed-off-by: moraaar moraaar@amazon.com

Code/Framework/AzToolsFramework/AzToolsFramework/API/EditorPythonConsoleBus.h

@@ -70,8 +70,12 @@ namespace AzToolsFramework
         //! Determines if the caller needs to wait for the Python VM to initialize (non-main thread only)
         virtual void WaitForInitialization() {}
 
-        //! Acquires the Python global interpreter lock (GIL) and executed the callback
+        //! Acquires the Python global interpreter lock (GIL) and execute the callback
         virtual void ExecuteWithLock(AZStd::function<void()> executionCallback) = 0;
+
+        //! Tries to acquire the Python global interpreter lock (GIL) and execute the callback.
+        //! @return Whether it was able to lock the mutex or not.
+        virtual bool TryExecuteWithLock(AZStd::function<void()> executionCallback) = 0;
     };
 
     //! A bus to handle post notifications to the console views of Python output