Reverse the Order of Deinitialization for Allocated Struct Members

[cellomath]

I want to use zware for a memory-constrained embedded project.
Unwinding objects's allocations will allow for allocated memory to be more reusable, as FixedBufferAllocators can free its last allocated memory.

[malcolmstill]

@cellomath apologies for the delay in looking at this, thanks for the submission.

I think I understand the argument here and tests passing so will happily merge (though I might have to work through an example with FixedBufferAllocator to see a useful reuse without just throwing away the whole thing to completely understand).

If you could think up some test that checks this behaviour that might be nice to include to avoid future regressions.

Thanks!