[ObjC] Use NamedTypeReference to refer to id / SEL / BOOL

[bdash]

Rather than introducing duplicate definitions of these types, use a NamedTypeReference that will be resolved to the type from the libobjc type library when it is loaded.

This prevents these types from showing up as id_1 / SEL_1 in some places rather than as their expected names.

Fixes #7061.

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I tried about 5 different ways of referencing a type by name and this is the only one that seemed to work correctly:

NamedTypeReferenceBuilder builder;
builder.SetName(QualifiedName(name));
return Type::NamedType(builder.Finalize());

I'm not really clear why that works but Type::NamedType(m_data, name) doesn't.