Improve the OOP ABI

[Adam D Ruppe]

On Thursday, 28 September 2023 at 13:05:01 UTC, Richard (Rikki) 
Andrew Cattermole wrote:
> TypeInfo isn't guaranteed to be unique to a process when 
> dealing with shared libraries. There is a strong chance it'll 
> be duplicative.

This should be fixed, but even if it isn't, that just means using 
the ==  operator instead of the is operator; the concept i 
believe is still sound.

(the == operator sux tho, this really should be fixed at the 
source)

> ClassInfo is an alias to TypeInfo_Class now. This indirection 
> shouldn't exist.

this means emplacing the typeinfo_class in the same memory block 
as the vtbl instead of linking to it.

so the virtual table exists at *(instance + 
__traits(classInstanceSize, TypeInfo_Class))