Add support for multiple LOCAL_COMPATIBILITY_SUITES & undefined testcase directories.

1) Updates the LOCAL_COMPATIBILITY_SUITE line to allow for a
   testcase to belong to multiple suites.
2) Building testcases no longer fails if
   COMPATIBILITY_TESTCASES_OUT_<suite> is not defined. This
   testcase will just not output to that directory.
   This will be utilized by the device-tests and general-tests
   suites that don't require any extra output besides the common
   testcase directory.

Bug: 35394351
Test: 1) Added multiple *TS testcases to cts & vts and verified they
       ended up in the common directory and each suite's testcase
       directory. Specifically tested CtsSplitApp to ensure the
       split usecase still works as well.
      2) Added a CTS testcase to the device-tests suite, built
       device-tests and verified the cts/android-cts/testcases
       copy was not produced.

Change-Id: Ic4c4e87e62be4fc0c5e394d88cc359518346dffa
(cherry picked from commit 6bea37c7)
Merged-In: Ic4c4e87e62be4fc0c5e394d88cc359518346dffa