Migrate to karma-sabarivka-reporter

Originally, this project (edx/ecommerce) was using `karma-coverage-allsources` to
include all project files under coverage statistic. However, this
package seems to be abandoned as well as close source and with security
issues https://snyk.io/test/npm/karma-coverage-allsources. With this commit, ecommerce
project now uses compatible open source alternative [karma-sabarivka-reporter](https://github.com/kopach/karma-sabarivka-reporter).
Which is writtent in TS, 100% tested and has no known security issues
https://snyk.io/test/npm/karma-sabarivka-reporter