Enhance cetl::pmr::Factory::make_unique to support "interface/concrete" scenario.

[serges147]

1. Currently you have to do something like this:

template <typename Tag, typename... Args>
CETL_NODISCARD UniquePtr<typename Tag::Interface> makeUniquePtr(cetl::pmr::memory_resource& memory, Args&&... args)
{
    PmrAllocator<typename Tag::Concrete> allocator{&memory};
    auto interface_deleter = typename UniquePtr<typename Tag::Interface>::deleter_type{allocator, 1};

    auto concrete  = cetl::pmr::Factory::make_unique(allocator, std::forward<Args>(args)...);
    auto interface = UniquePtr<typename Tag::Interface>{concrete.release(), interface_deleter};

    return interface;
}

2. The above code has issue with cetl::pmr::memory_resource, namely incorrect size on deallocation (8 bytes instead of real/concrete size which was during allocate).