[3.6] Move Codecov's configuration file under .github (GH-1494) (GH-1574)

(cherry picked from commit cbddf58c797f850a5b06f317a4bb7ab69c6e9715)
diff --git a/.codecov.yml b/.github/codecov.yml
similarity index 100%
rename from .codecov.yml
rename to .github/codecov.yml