Create a separate coverage target for Cronet tests

This will allow us add more java test targets without need to change
mts-tethering-coverage. Also in tune with the current Connectivity
setup.

Will consider merging to ConnectivityCoverageTests afterwards.

Bug: 263294440
Test: atest NetHttpCoverageTests
Change-Id: I4f65b30ccf548cc7f278488d73fe9e733a9c608d
4 files changed