Adds CTS tests for `urEnqueueUSMMemset2D` entry-point

[veselypeta]

We should add conformance tests for urEnqueueUSMMemset2D.

Required Coverage:

• At least one successful (i.e. called with correct arguments and assert on expected result, not applicable to CreateWithNativeHandle entry points)
• If this a query entry-point or one which accepts flags etc : we should tests every possible enumeration (where possible).
• A test case for each returned error code (exclude disaster situations i.e. OUT_OF_MEMORY etc)

[fabiomestre]

Done in #297