Adding Avito-provided code to init the repository

Avito has generously provided some sample code (sample.py) to start
the competition as well the grading scheme (APatK) they will use
for evaluation. Files have been renamed but are otherwise untouched.

Closes task #14800544868583
Modify sample.py to account for new folder scheme

Modified the original sample.py to get it running in the new folder
scheme for this project. The scheme is outlined in the README. Second
modification was to switch the code to using .tsv files over .pkl,
since those are the sources we have available.

APatK.py was untouched as it's useless on its own anyways. Without
the 'correct' comparison data it is purely an illustration of AP@k.

Closes task #14800544868586