Build disabled CUB tests (CDP tests remain)

[alliepiper]

There are a number of tests that we currently aren't building because they are ifdef'd out -- @senior-zero discovered a few uncovered cases in test_block_scan, and @canonizer just reported another in test_device_radix_sort.

Grepping through, I found the following similar issues listed below. We should get these working.

Block radix sort appears to be skipping some SortKeys tests::

• [x] test_block_radix_sort.h:#ifdef TEST_KEYS_ONLY

Block reduce isn't testing anything:

• [x] test_block_reduce.cu:#ifdef TEST_RAKING
• [x] test_block_reduce.cu:#ifdef TEST_WARP_REDUCTIONS

Block scan isn't testing anything:

• [x] test_block_scan.cu:#ifdef TEST_RAKING
• [x] test_block_scan.cu:#ifdef TEST_RAKING_MEMOIZE
• [x] test_block_scan.cu:#ifdef TEST_WARP_SCANS

DeviceSegmentedRadixSort is untested:

• [x] test_device_radix_sort.cu:#ifdef SEGMENTED_SORT

Lots of missing CDP tests:

• [ ] test_device_radix_sort.cu: #ifdef CUB_CDP
• [ ] test_device_reduce.cu:#ifdef CUB_CDP
• [ ] test_device_reduce_by_key.cu:#ifdef CUB_CDP
• [ ] test_device_run_length_encode.cu:#ifdef CUB_CDP
• [ ] test_device_scan.cu:#ifdef CUB_CDP
• [ ] test_device_scan_by_key.cu:#ifdef CUB_CDP
• [ ] test_device_select_if.cu:#ifdef CUB_CDP
• [ ] test_device_select_unique.cu:#ifdef CUB_CDP
• [ ] test_iterator.cu:#if CUB_CDP Note that this should be ifdef

[alliepiper]

NVIDIA/cub#403 addresses everything but the CDP tests.