cubicweb #4601327 Add way of debugging HTML generation [validation pending]

There should be a way of easily knowing what piece of code was involved in generating a particular piece of HTML source code.

prioritynormal
typeenhancement
done in3.20.0
load0.500
load left0.000
closed by#0aebb1c0f849 [utils] Add a '_cwtracehtml' GET parameter to trace self._cw.w() calls (closes #4601327)
patch[utils] Add a '_cwtracehtml' GET parameter to trace self._cw.w() calls (closes #4601327) [applied]