Fix instabilities in Velo CPU ci-tests (v3)

Locally it doesn't seem to fluctuate. To be tested in the ci. Some minor changes are expected due to differences between the vectorized CPU code and the GPU code. Throughput is expected to drop a bit only for the CPU test.

Drop the specialized vectorized velo seeding function for CPU.

Closes Moore#607 (closed) Moore#769 (closed)

FYI @dovombru @cagapopo @jonrob @cmarinbe