Add commands to make jdwp tests dump stacks on timeouts

Debugging timeouts of jdwp tests is very difficult because we don't
have any real information to use. To help with debugging we added
support for dumping the threads of the debuggee processes using
debuggerd and kill -3.

Test: modify a test with infinite loop, Run
Bug: 70838465
Change-Id: I7d4f17d28b6a30553dfc79884680381a626fb5af