Image Metadata

With #882 clspv will have a first basic support of `get_image_channel_order` and `get_image_channel_data_type`.
This support uses the `pod_pushconstant`.

Here is what is left to do to have a better support:
- [ ] allow to pass those metadata through UBO instead of pod pushconstant (both should be possible. The one used for an execution would depend on the kernel).
- [ ] At the moment, those metadata can exceed the max push constant size without having clspv knowing about. We would need to deal with that. Passing it by UBO instead could be a possibility.