[Feature] Changes to H&F timing

[CCuskley]

We currently have 12 hearts, 16 flowers, and 32 mixed trials. We propose splitting the 32 mixed into two blocks of 16 (overall "mixed" blocks 3 and 4), with the third block with a 2s timeout, and the fourth block where the timeout is either 1s or 2s or 3s (which of those three it is depends on the theta estimate right before the fourth block starts)