oss/github: Use codecov github action
oss/github: Use codecov github action

Problem/Solution

Instead of curling and executing a script,
integrating the codecov recommended github action.
https://github.com/codecov/codecov-action

JIRA Issues: CSL-11181

Differential Revision: https://phabricator.twitter.biz/D710862

twitter/finatra,twitter/finatra,twitter/finatra