bugfix: pass down trial parameter to subclass.

[pellet]

bugfix: pass down trial parameter to subclass as was previously done before VR code modified rendering logic.

Also fixed baseclass 'present_stimulus' method signature to match arguments as expected for subclass to implement.

This was something which I accidentally had modified the behaviour of - I had trouble understanding what the 'trial' parameter was used for in the experiments.
It seems like none of the example experiments are using the parameter.

[JohnGriffiths]

@pellet - summary from discussion:

looks like the trial variable actually wasn't ever being used

could you please first check that in the rest of the code and confirm

if so, update this PR to remove that variable entirely as it's redundant

thanks

[JohnGriffiths]

@pellet as discussed - I want to give this a spin in a few more contexts before merging.

I think you're right that this does leave things in a better state than they currently are.

Noting - the main issue to consider here now is actually not the trial parameter, but the behaviour of the audio device, which is also fixed in this PR. But, it was behaving weirdly for me in testing just now.

And it looks like the audio device in general may have suffered some recent breakages we haven't yet fully clocked.