Move call to ApiVulkanSample::submit_frame to after submitting both graphics command buffers

[asuessenbach]

Description

Fixes validation layer error

vkQueueSubmit(): pSubmits[0] performs a layout transition on presentable VkImage 0x50000000005, but the image has not been acquired from VkSwapchainKHR 0x40000000004 (either never or since the last present operation).
The Vulkan spec states: Use of a presentable image must occur only after the image is returned by vkAcquireNextImageKHR, and before it is released by vkQueuePresentKHR. This includes transitioning the image layout and rendering commands (https://docs.vulkan.org/refpages/latest/refpages/source/VkSwapchainKHR.html#_description)

Build tested on Win11 with VS2026. Run tested on Win11 with NVidia GPU.

Note: the left upper part of the window shows a smaller view of the graphics window, its size depends on the "Subpass size reduction" control, hiding parts or all of the GUI. Is that intended?

General Checklist:

Please ensure the following points are checked:

• My code follows the coding style
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• My changes do not add any new validation layer errors or warnings
• I have used existing framework/helper functions where possible
• My changes do not add any regressions
• I have tested every sample to ensure everything runs correctly
• This PR describes the scope and expected impact of the changes I am making

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• I have updated the header Copyright to reflect the current year (CI build will fail if Copyright is out of date)
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If this PR contains framework changes:

• I did a full batch run using the batch command line argument to make sure all samples still work properly

Sample Checklist

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• I have tested the sample on at least one compliant Vulkan implementation
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[tomek-brcm]

Not supported for Broadcom