[lldb] Add ScriptedPlatform python implementation

This patch introduces both the Scripted Platform python base
implementation and an example for it.

The base implementation is embedded in lldb python module under
`lldb.plugins.scripted_platform`.

This patch also refactor the various SWIG methods to create scripted
objects into a single method, that is now shared between the Scripted
Platform, Process and Thread. It also replaces the target argument by a
execution context object.

Differential Revision: https://reviews.llvm.org/D139250

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

lldb/source/Plugins/ScriptInterpreter/Python/ScriptedProcessPythonInterface.cpp

@@ -37,16 +37,18 @@ StructuredData::GenericSP ScriptedProcessPythonInterface::CreatePluginObject(
   if (class_name.empty())
     return {};
 
-  TargetSP target_sp = exe_ctx.GetTargetSP();
   StructuredDataImpl args_impl(args_sp);
   std::string error_string;
 
   Locker py_lock(&m_interpreter, Locker::AcquireLock | Locker::NoSTDIN,
                  Locker::FreeLock);
 
-  PythonObject ret_val = LLDBSwigPythonCreateScriptedProcess(
-      class_name.str().c_str(), m_interpreter.GetDictionaryName(), target_sp,
-      args_impl, error_string);
+  lldb::ExecutionContextRefSP exe_ctx_ref_sp =
+      std::make_shared<ExecutionContextRef>(exe_ctx);
+
+  PythonObject ret_val = LLDBSwigPythonCreateScriptedObject(
+      class_name.str().c_str(), m_interpreter.GetDictionaryName(),
+      exe_ctx_ref_sp, args_impl, error_string);
 
   m_object_instance_sp =
       StructuredData::GenericSP(new StructuredPythonObject(std::move(ret_val)));