[Feature] DaedalusSymbol: Expose OffsetAsMember and ClassSize for instance addressing

[JaXt0r]

When Ikarus scripts allocate a struct with MEM_Alloc and access its fields through a transient instance, each field's byte position within the allocation must be computed. This requires two symbol metadata values that are available in the C++ API but not yet exposed in the C# wrapper.

Reference OpenGothic (directmemory.cpp):

void memory_instance::set_int(const zenkit::DaedalusSymbol& sym, uint16_t index, int32_t value) {
    ptr32_t addr = address
                 + ptr32_t(sym.offset_as_member()) // 1.
                 + ptr32_t(index * sym.class_size());  // 2.
    owner.mem32.writeInt(addr, value);
}

Requested C# API:

• DaedalusSymbol.OffsetAsMember
• DaedalusSymbol.ClassSize