Remove junit-runner and revert files to standard JUnit 4.10

Removes the junit-runner target as it is no longer used, the
junit-runner-files variable and removes any Android specific
patches needed to maintain backwards compatibility with the
Android API. That includes the removal of TestSuiteLoader and
StandardTestSuiteLoader as they are not part of JUnit 4.10
and only kept to maintain compatibility with the Android API.

This will not affect the Android API as that is now generated
from copies of the files in frameworks/base/test-runner/src/.

Bug: 30188076
Test: make checkbuild
Change-Id: I53c138cdd8b33a5b9ec1e8c16f3dde637762c0fc