Add fallback for AMD shader core count without shader core properties2

[rasbid]

Summary

• track the VK_AMD_shader_core_properties device extension during enumeration
• add the AMD shader core properties struct to the property query chain and compute shader core counts as a fallback when the v2 extension is absent

Testing

• not run (not requested)

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https://chatgpt.com/codex/tasks/task_e_68ebe81407f0833085d10eb6791d5e98