Vulkan test on linux.

[takahiroharada]

This pull request introduces a new Vulkan/HIP external memory interoperability demo (VulkanComputeSimple) and updates the build system to conditionally include the demo and its unit test only when Vulkan headers are available. The changes ensure that the demo is built and tested on both Windows and Linux, with robust handling for header dependencies.

Key changes:

VulkanComputeSimple demo addition and documentation

• Added a new VulkanComputeSimple demo showcasing Vulkan/HIP external memory interop, including a comprehensive README.adoc with build and usage instructions.

Build system improvements for conditional demo inclusion

• Updated the main premake5.lua workspace script to detect the presence of Vulkan headers (via Windows, LunarG SDK, or system headers) and set a buildVulkanDemo flag. The demo and its test are only included if this flag is set, with a clear message if skipped.
• Modified the VulkanComputeSimple demo's premake5.lua to use system or SDK Vulkan headers on Linux, and to only add Windows-specific build options and links when building for Windows.
• Updated the unit test project (UnitTest/premake5.lua) to define ORO_HAS_VULKAN_DEMO only if the demo is being built, ensuring the test is conditionally compiled.

Unit test conditional compilation

• Changed the registration of the VulkanComputeSimple64 unit test in demosTest.cpp to depend on the ORO_HAS_VULKAN_DEMO define, so the test is only present when the demo is built. [1] [2]