discover gpu resizable bar feature, faster weight upload

[nihui]

z-image-ncnn 1024x1024

end2end	7900xtx
baseline	39.70s
+rebar	38.35s

[tencent-adm]

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 67.56757% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.94%. Comparing base (7d5d32d) to head (3918855).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/allocator.cpp	25.00%	9 Missing ⚠️
src/gpu.cpp	88.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6536      +/-   ##
==========================================
- Coverage   92.94%   92.94%   -0.01%     
==========================================
  Files         809      809              
  Lines      256714   256613     -101     
==========================================
- Hits       238613   238508     -105     
- Misses      18101    18105       +4     

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[Copilot]

Pull request overview

Adds a Vulkan-side capability probe for “Resizable BAR” (approximated via memory property inspection) and uses it to prefer more upload-friendly memory types for weight buffers/images to improve end-to-end performance.

Changes:

• Expose GpuInfo::resizable_bar_enabled() as a new GPU property.
• Cache/query physical device memory properties during GPU init and log rebar status.
• Adjust VkWeightAllocator memory-type selection to prefer device-local + host-visible allocations when ReBAR is detected.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/gpu.h	Adds GpuInfo::resizable_bar_enabled() API.
src/gpu.cpp	Implements memory-property query and derives/logs the ReBAR flag.
src/allocator.cpp	Uses the ReBAR flag to tweak weight allocation memory preferences.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

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