Add tests for DDM 'connected' & 'disconnected' calls

These functions of ChunkHandler need to be called on the first
DDM.Chunk call and the 'disconnected' function is to be called when
the debugger disconnects if the connected function has been called.
This adds verification of this behavior.

Bug: 62821960
Bug: 69169846

Test: ./art/tools/run-jdwp-tests.sh --mode=host
Test: ./art/tools/run-libjdwp-tests.sh --mode=host
Change-Id: Iccb291be76c2553eabf98815703e2b13dccc0c99