Output *TS testcases to their own subdir in the common testcase folders.

Instead of dumping all *TS testcases into the common testcase
directory directly, place them all in their own subdirectory.

Bug: 35153177
Test: `make cts -j` and checked the contents of both:
out/host/linux-x86/testcases/ &
out/host/linux-x86/cts/android-cts/testcases/

Change-Id: I22a768dba58d40be1e61885534fb813e7ff08c99
(cherry picked from commit 3fb354cc)
Merged-In: I22a768dba58d40be1e61885534fb813e7ff08c99