honor vulkan extension dependencies

[nihui]

No description provided.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 38.37209% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.56%. Comparing base (8775d9c) to head (e288f6c).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/gpu.cpp	38.37%	53 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6705      +/-   ##
==========================================
- Coverage   93.95%   93.56%   -0.39%     
==========================================
  Files         933      933              
  Lines      299683   299358     -325     
==========================================
- Hits       281556   280104    -1452     
- Misses      18127    19254    +1127     

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[Copilot]

Pull request overview

Updates NCNN’s Vulkan capability detection to better respect extension dependency chains, and adds tracking/enabling for device-group related extensions.

Changes:

• Add instance-level tracking for VK_KHR_device_group_creation and device-level tracking/accessor for VK_KHR_device_group.
• Introduce dependency-based filtering to mask out extensions whose prerequisites are not met.
• Enable VK_KHR_device_group_creation at instance creation and VK_KHR_device_group at device creation when supported.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/gpu.h	Declares new Vulkan extension support globals and a new GpuInfo accessor for device-group support.
src/gpu.cpp	Implements new extension support variables, dependency filtering, instance/device extension enabling, and the new GpuInfo accessor.

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