[lldb] Add #include <optional> (NFC)

This patch adds #include <optional> to those files containing
llvm::Optional<...> or Optional<...>.

I'll post a separate patch to actually replace llvm::Optional with
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

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

@@ -20,6 +20,7 @@
 #include "ScriptInterpreterPythonImpl.h"
 #include "ScriptedProcessPythonInterface.h"
 #include "ScriptedThreadPythonInterface.h"
+#include <optional>
 
 using namespace lldb;
 using namespace lldb_private;