1) Moved the patched junit code in test-base and test-runner to a new directory test-junit which is under license CPL-1.0.
2) Clean the license metadata on packages in test-base, test-mock, test-runner and test-junit so packages have their license metadata precisely.
3) With this cleanup the Android.mk in test-legacy could be converted to Soong with license metadata handled properly, see b/319031379 and aosp/2900169.

Bug: 328809280
Test: CIs
Change-Id: I2a5832a97b09a5c7d064b8c2adbc0b04a325f326