Turn uses of `COVERAGE_PATHS` and `COVERAGE_EXCLUDE_PATHS` into errors.

All known uses of environment variables `COVERAGE_PATHS` and
`COVERAGE_EXCLUDE_PATHS` have been replaced with
`NATIVE_COVERAGE_PATHS` and `NATIVE_COVERAGE_EXCLUDE_PATHS` (resp.).

Test: m nothing
Test: Check that `m nothing COVERAGE_PATHS=art` fails.
Test: Check that `m nothing COVERAGE_EXCLUDE_PATHS=art` fails.
Test: Check the Android Build for build errors related to these variables.
Bug: 158212027
Change-Id: Icc7c1d9734e78c2bf327f00f04355700b5476648