Fix stacks for Java processes.

Fix stacks for the change in ANR trace location by using `debuggerd -j`
instead of manually fetching the traces file.

Also, dump zygote/zygote64 as native processes, since they don't
respond to SIGQUIT.

Test: stacks zygote
Test: stacks adbd
Test: stacks com.android.settings
Change-Id: I015458bdc2dd45624940204d42614365aacf8304