Revert D23379383: Land `code_coverage_tool` to `caffe2/tools` folder
Test Plan: revert-hammer
Differential Revision:
D23379383 (https://github.com/pytorch/pytorch/commit/f06d3904f2c7b6e47ffa532f4a22b9e18941bb90)
Original commit changeset: f6782389ebb1
fbshipit-source-id: 33a26761deb58dfe81314ea912bf485c5fc962b7
