Itanium RTTI metadata not symbolized when base type info is extern

[emesare]

Regression from 5.2 that affects VMI class type that has the base type info in another binary (e.g. extern)

1. Open loss publish wander
2. Go to 0x100620e58
3. Observe that there is no symbol named _typeinfo_for_DetailsTab

Was caused by new GNU3 demangler changing the naming scheme for the extern symbol:

Old: _typeinfo_for_QTabWidget
New typeinfo_for_QTabWidget

So just need to update this code here:

binaryninja-api/plugins/rtti/itanium.cpp

Lines 448 to 451 in 24eabc0

	// Remove type info prefix.
	if (symName.rfind("_typeinfo_for_", 0) != 0)
	return std::nullopt;
	return symName.substr(14);