[TEST] Run urUSMContextMemcpyExpTestDevice to reproduce #19688
This is a test PR to verify if the sporadic failure in issue #19688
can be reproduced on CI.
Changes:
- Remove UUR_KNOWN_FAILURE_ON(uur::CUDA{}) to enable the test
- Add loop with 20 iterations to increase probability of hitting
the race condition
- Re-initialize allocations between iterations
