[lldb] Use std::optional instead of llvm::Optional (NFC)

This patch replaces (llvm::|)Optional< with std::optional<.  I'll post
a separate patch to clean up the "using" declarations, #include
"llvm/ADT/Optional.h", etc.

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/ScriptedPythonInterface.cpp

@@ -80,9 +80,9 @@ ScriptedPythonInterface::ExtractValueFromPythonObject<lldb::DataExtractorSP>(
 }
 
 template <>
-llvm::Optional<MemoryRegionInfo>
+std::optional<MemoryRegionInfo>
 ScriptedPythonInterface::ExtractValueFromPythonObject<
-    llvm::Optional<MemoryRegionInfo>>(python::PythonObject &p, Status &error) {
+    std::optional<MemoryRegionInfo>>(python::PythonObject &p, Status &error) {
 
   lldb::SBMemoryRegionInfo *sb_mem_reg_info =
       reinterpret_cast<lldb::SBMemoryRegionInfo *>(