Rename Runner to TargetRunner

This is in preparation for switching over to using standard
junit. JUnit has its own Runner class that does something
reasonably similar but not the same so this should avoid
confusion while making the switch over. Eventually, the
TargetRunner classes will be replaced with ones based off JUnit.

Bug: 27940141
Change-Id: I3327ff2fb0947bf22038a8db1603daa8420b78ee
10 files changed