Loader Settings: Invalid `deviceUUID` report a warning and exit

Using the following `vk_loader_settings.json`:

[vk_loader_settings.json](https://github.com/user-attachments/files/21386245/vk_loader_settings.json)

I am using `"additional_drivers_use_exclusively": true` because of https://github.com/KhronosGroup/Vulkan-Loader/issues/1718 bug

But here I am using un invalid `deviceUUID` leading to not finding the device.

Running `vulkaninfoSDK`, I am getting the following log:

```
Launching Vulkan Application:
- Executable: E:\VulkanSDK\1.4.321.0-rc\Bin\vulkaninfoSDK.exe
- Working Directory: C:\Users\Piranha\VulkanSDK
- Command-line Arguments:
- --summary
- Log file: C:\Users\Piranha\VulkanSDK\vulkaninfo.txt

WARNING: [Loader Message] Code 0 : Layer VK_LAYER_NV_optimus uses API version 1.3 which is older than the application specified API version of 1.4. May cause issues.

WARNING: [Loader Message] Code 0 : loader_apply_settings_device_configurations: settings file contained device_configuration which does not appear in the enumerated VkPhysicalDevices. Missing VkPhysicalDevice with deviceName: "llvmpipe (LLVM 20.1.6, 256 bits)" and deviceUUID: 6e667462-3336-2f31-2f38-111111

Process terminated
```

If the behavior is to exit the program, I would suggest to report an error. Another approach could be to ignore the the `device_configurations` and report the warning.

Start with loader_apply_settings_device_configurations and reproduce the invalid deviceUUID case using the linked vk_loader_settings.json through vulkaninfoSDK. Determine whether the intended result is an error and exit or a warning that ignores the device_configuration; done means the chosen behavior is implemented and covered by regression testing.

Written by the indexing model from the issue text.