Refactor python execution counter

[tamarinvs19]

Description

Now we have an additional counter of generated executions (50000) because of problem from #1925. We need to reduce occupied by UtFuzzedExecution space and remove the counter.
One of the problems with the execution counter is non-use all time and too early completion.

Expected behavior

For example, see #1925. No errors with memory but without a special counter, utbot uses all time.