ENHANCED: time/1 now shows the number of inferences

[triska]

I'm marking this as a draft because it does not yet show the number of inferences when the goal fails.

[triska]

In addition, nested time/1 calls do not yet work with these changes:

:- time(use_module(library(lists))).
   % 0.000s CPU, 20 inferences
?- time(time(member(X, "abc"))).
   % 0.000s CPU, 2 inferences
   % 0.000s CPU, 2_202 inferences
   X = a
;  % 0.000s CPU
   error(representation_error(inference_limit),time/1), unexpected.

Update: Nested calls are now addressed.

[triska]

Please see #2009 for the issues I encountered with the current approach. I think a separate internal inference counter is needed.

[mthom]

I updated my copy of this PR branch with changes at https://github.com/mthom/scryer-prolog/tree/triska-time_inferences, please try it and give feedback.

[triska]

I have updated the branch, using the newly available inference counting feature.

Some fine-tuning may be appropriate for specific cases such as ?- time(false)., though it is not clear to me where this tuning should happen: in the internal inference counting mechanism, or in library(time).

Please review, and merge if applicable. Thank you a lot!