Add class-safe image suballocation

[antono3]

Summary

• add explicit opt-in suballocation APIs for ordinary linear and optimal images
• isolate reusable blocks by Vulkan memory type and resource class, eliminating mixed-class bufferImageGranularity boundaries
• honor Vulkan 1.1 required and preferred dedicated allocations, with a conservative Vulkan 1.0 fallback
• expose resource classes in allocation records, diagnostics, and filtered fragmentation statistics
• reject sparse, disjoint, and DRM-format-modifier images from the ordinary binding path
• add deterministic mixed-class stress coverage and a real lavapipe image-sharing example
• run every Vulkan CI workload with the Khronos validation layer

The existing create_image* APIs retain dedicated-allocation behavior. Image sharing is additive and explicit through create_suballocated_image*.

Validation

• exact V 0.5.2 (7647ce1) format and vet
• exact V 0.5.2 setup check and 7/7 allocator test files
• exact V 0.5.2 ASan + UBSan test suite
• lavapipe buffer, image, and sustained-stress examples with VK_LAYER_KHRONOS_validation
• real image smoke: two optimal images shared one block at offsets 0 and 16384; a linear image and buffer used separate blocks