[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/ScriptInterpreterPython.cpp

@@ -50,6 +50,7 @@
 #include <cstdlib>
 #include <memory>
 #include <mutex>
+#include <optional>
 #include <string>
 
 using namespace lldb;