[WIP/blocked] Factor out runner._report_for_call, using item._current_callinfo

[blueyed]

Ref: pytest-dev#5996 (comment)

TODO:

• Revert "Node from parent (#5975)" #143 ?
• re-add test? pytest-dev@847eace#diff-b4fb7e39b215eabeb6a34d130d8aef2dL504-L511
• check/verify rebase ( b1cee40 to 4d578fa )

[RonnyPfannschmidt]

this is a creative way to sort out the different interaction pattern that unit-test brings about

i hope that my fear is unwarranted (and just a remnant of past changes)

as always, naming is the most difficult

thanks for starting this POC

[RonnyPfannschmidt]

this structure changes a CallInfo from something concrete and state-free to a state-machine tracking the progress if a call

i believe a class name change is warranted to make this clear, but off hand no good name describing it comes to mind