[BUG] Shuffle partitions for the first GPU run should not be set for more than 200

[kuhushukla]

Describe the bug
In order to fully utilize the benefits of multithreaded shuffle, the first GPU run (when autotuner runs on cpu logs) should not increase partitions to values > 200.

We might have to fork this logic for GPU iterations where the benefit of higher partitions overrides the ones from MT shuffle.

[mattahrens]

Scope: update auto-tuner to detect that it is processing a CPU event log and then default shuffle partitions to 200. When GPU event log is detected, it can keep existing logic.