Add device_generated_commands_query extension sample (VK_NV vs VK_EXT fallback)

[batoripX]

Description

Adds a new extension sample (device_generated_commands_query) demonstrating how to handle architectural and structural disparities between legacy vendor-specific VK_NV_device_generated_commands and the modern unified cross-vendor VK_EXT_device_generated_commands specification.

Tested locally on NVIDIA Ampere (RTX 3050) hardware where legacy VK_NV is exposed.

General Checklist:

• My code follows the coding style
• I have reviewed file licenses (Apache 2.0 / SPDX headers included)
• My changes do not add any new compiler warnings
• My changes do not add any new validation layer errors or warnings
• I have tested every sample to ensure everything runs correctly
• This PR describes the scope and expected impact of the changes I am making
• I have updated the header Copyright to reflect the current year (2026)

Sample Checklist:

• I have tested the sample on at least one compliant Vulkan implementation (RTX 3050 / Windows)
• If the sample is vendor-specific, I have tagged it appropriately
• I have stated on what implementation the sample has been tested (NVIDIA Ampere RTX 3050)

[CLAassistant]

All committers have signed the CLA.

[SaschaWillems]

So where is the actual sample in this PR? Looks like this is missing some (or all) relevant files.