Stevens should not have limit on input per subcondition

[coyiutoc]

Currently the implementation is that once a user makes an input 4 times, the experiment moves to the next subcondition.

I am assuming that the correct behavior is that:

• trials_per_round indicates the number of times a subcondition REPEATS (i.e if trials_per_round = 4, the same subcondition repeats 4 times). This is based on observations from the participant data of stevens from the original codebase.
• user can input indefinite number of key presses for a given round in a subcondition.
• once user is happy with their estimate, spacebar input will move experiment to the next round of the same subcondition, or onto the next subcondition if the number of rounds = trials_per_round.

[coyiutoc]

Resolved: https://github.com/coyiutoc/VCL_Correlation_POC/commit/2404de711ad5db8bfdf8181fee172797eb8f34ef

** Included into this fix is also refactoring done for stevens export + practice trial refactoring.