bpo-43950: implement on-the-fly source tracking for interactive mode

[isidentical]

Purely for design purposes, do not review/merge.

https://bugs.python.org/issue43950

[isidentical]

One problem with this patch is that, we need to limit fetching from __source__ only for the main frame, otherwise if the offsets match out it will show something like this;

 $ ./pythonPython3.11.0a0 (heads/[bpo-43950](https://bugs.python.org/issue43950)-source-tracking-dirty:1173c11e09, Jul172021, 14:52:40) [GCC9.3.0] onlinuxType"help", "copyright", "credits"or"license"formoreinformation. >>>defframe_3(): ... return1/0 ... >>>defframe_2(): ... returnframe_3() ... >>>defframe_1(): ... returnframe_2() ... >>>ifTrue: ... 1+frame_1() ... Traceback (mostrecentcalllast): File"<stdin>", line2, in<module>1+frame_1() ^^^^^^^^^File"<stdin>", line2, inframe_11+frame_1() ^^^^^^^^^File"<stdin>", line2, inframe_21+frame_1() ^^^^^^^^^File"<stdin>", line2, inframe_31+frame_1() ^^^ZeroDivisionError: divisionbyzero

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[CAM-Gerlach]

Hey @isidentical , can this be closed now?

[isidentical]

Thanks for the reminder @CAM-Gerlach, this was mainly an experiment before it ever got to be a real PR so yep we can close it.