[lldb/Interpreter] Fix deep copying for OptionValue classes

Some implementations of the DeepCopy function called the copy constructor that copied m_parent member instead of setting a new parent. Others just leaved the base class's members (m_parent, m_callback, m_was_set) empty.
One more problem is that not all classes override this function, e.g. OptionValueArgs::DeepCopy produces OptionValueArray instance, and Target[Process/Thread]ValueProperty::DeepCopy produces OptionValueProperty. This makes downcasting via static_cast invalid.

The patch implements idiom "virtual constructor" to fix these issues.
Add a test that checks DeepCopy for correct copying/setting all data members of the base class.

Differential Revision: https://reviews.llvm.org/D96952

lldb/source/Interpreter/OptionValueFileColonLine.cpp

@@ -134,10 +134,6 @@ Status OptionValueFileColonLine::SetValueFromString(llvm::StringRef value,
   return error;
 }
 
-lldb::OptionValueSP OptionValueFileColonLine::DeepCopy() const {
-  return OptionValueSP(new OptionValueFileColonLine(*this));
-}
-
 void OptionValueFileColonLine::AutoComplete(CommandInterpreter &interpreter,
                                             CompletionRequest &request) {
   CommandCompletions::InvokeCommonCompletionCallbacks(