Terminal: Enable TerminalProcessInterface

Adds a new helper app "process_stub" that replaces the previous.
"process_stub_unix/win". The purpose was and is to allow processes
to be "injected" into other hosts apps like terminals while still
being able to control and debug them.

A new base class called "TerminalInterface" is used for both the new
Terminal plugin and the legacy TerminalProcess implementation.

Fixes: QTCREATORBUG-16364
Change-Id: If21273fe53ad545d1a768c17c83db4bf2fd85395
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/terminal/terminalprocessimpl.h

@@ -0,0 +1,18 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0+ OR GPL-3.0 WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include "terminalpane.h"
+
+#include <utils/terminalinterface.h>
+
+namespace Terminal {
+
+class TerminalProcessImpl : public Utils::TerminalInterface
+{
+public:
+    TerminalProcessImpl(TerminalPane *terminalPane);
+};
+
+} // namespace Terminal