[lldb/Interpreter] Introduce ScriptedPlatform{,Python}Interface

This patch introduces both the ScriptedPlatformInterface and the
ScriptedPlatformPythonInterface. As the name suggests, these calls will
be used to call into the Scripted Platform python implementation from
the C++ Scripted Platform plugin instance.

Differential Revision: https://reviews.llvm.org/D139251



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>