Add device-tests and general-tests make targets.

Adds the device-tests and general-tests makefiles and
added include lines to main.mk so that individual test
modules can be built properly.

These targets do not build any special tradefed wrapper
that normal *TS's usually employ. They are not necessary
here.

Bug: 35350788
Test: Updated several CTS test modules to belong to these
      suites instead and ran:
      `rm -rf out; make clean; make device-tests general-tests -j`
      then verified the output.

Change-Id: I40e3958375f7b39cb56508f2812ce9760d403f6f