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/libs/utils/terminalhooks.h

@@ -6,6 +6,7 @@
 #include "commandline.h"
 #include "environment.h"
 #include "filepath.h"
+#include "id.h"
 
 #include <functional>
 #include <memory>
@@ -46,6 +47,7 @@ struct OpenTerminalParameters
     std::optional<FilePath> workingDirectory;
     std::optional<Environment> environment;
     ExitBehavior m_exitBehavior{ExitBehavior::Close};
+    std::optional<Id> identifier{std::nullopt};
 };
 
 struct NameAndCommandLine