Separate android.test.mock from test-runner source

Extracts the source for the android.test.mock library from the
frameworks/base/test-runner directory into its own
frameworks/base/test-mock directory. They are already treated separately
at runtime and compile time so this just makes the separation complete.

Bug: 30188076
Test: make checkbuild
Change-Id: I0489e33fc9aeac64420ec749fdd54b23f7f61222
Merged-In: I0489e33fc9aeac64420ec749fdd54b23f7f61222
(cherry picked from commit 490c6e403632962650c03b5b8ce1361f1848fe6e)
2 files changed