ur: add enqueue fill image

[veselypeta]

PI currently has an API function piEnqueueMemImageFill which is analogous to the openCL version clEnqueueFillImage

We should add this to Unified Runtime

[veselypeta]

Turns out this is already added to the spec, but does not appear in the generated header since it's not supported by level-zero
https://github.com/oneapi-src/unified-runtime/blob/main/scripts/core/enqueue.yml#L675

[kbenzie]

We should discuss why there are disabled entry points with the WG.

[kbenzie]

Along with urEnqueueMemImageFill, urEnqueueMemImageMap is also currently disabled.