Shader object layer settings should support vk_layer_settings.txt

[Jeremy Gebben]

This layer supports a setting called VK_SHADER_OBJECT_IGNORE_DRIVER_SUPPORT, but it only works as an environment variable.

It should be made to also use vk_layer_settings.txt and the android mechanism. They sync2 layer has a similar setting called VK_SYNC2_FORCE_ENABLE / khronos_synchronization2.force_enable.

Naming should also be made consistent with the sync2 layer.