Add VMA_RESULT for possible success codes

[YaaZ]

A new macro is used to document possible success codes for functions.
This may be useful just as a form of documentation, but even more useful for projects like VulkanMemoryAllocator-Hpp, which uses the VMA header to generate bindings, taking into account success codes when throwing exceptions.

[sawickiap]

I am sorry, but this proposal has been discussed and rejected already as #498.

[YaaZ]

Actually, I agree with your comment in #498, but my proposal is different in that it only includes success codes, not every code. With the same concerns:

creating and maintaining it would require a lot of work.

Not with the success codes.

Vulkan and DX12 functions are known to return error codes beyond the official list anyway

Should not be relevant if we limit the scope to success codes, right?

Whenever a specific returned value has a specific meaning (like in vmaFindMemoryTypeIndex), it is documented.

It's documented in a free form, what I propose is a strict format.

Interesting thing by the way: Vulkan-Hpp throws exceptions for error codes and VMA-Hpp currently does the same, but for vmaFindMemoryTypeIndex and similar functions, VK_ERROR_FEATURE_NOT_PRESENT is one of the normal results - it doesn't look to me like we should throw exception there. Although the result code indicates an error, semantically it's a status code.
So you've chosen the most suitable code you could find among existing codes, but did you originally consider this an error, or status code?

It seems, such confusion is a sign, that strict documentation of return codes could indeed be helpful, but if you reject my proposal, the discussion is still valuable in itself.

[sawickiap]

I am sorry but VMA is a C++ library with interface in C, while any binding to other programming languages are out of scope of this repository. To avoid feature creep, I don't want to make the code longer or more convoluted to support such bindings.