Make GenericMemoryAllocatorCreateInfo::block_sizes more flexible

[marc0246]

Changelog:

### Breaking changes
Changes to memory allocation:
- `GenericMemoryAllocatorCreateInfo::block_sizes` now represents a block size per memory type, instead of per memory heap, to allow for a more fine-grained configuration.

There wasn't really any reason block sizes would have to be restricted to the level of heaps. Apart from the added flexibility this also makes the code cleaner. I also merged the two lifetimes GenericMemoryAllocatorCreateInfo into one as I don't think it's needed, and replaced the use of ash::vk::MemoryPropertyFlags with our own. This was originally the ash type because before #2073, the ArrayVec would have taken up a huge amount of space, and would need a costly conversion to the bitfield anyway.