Notify system when uiAutomation terminates

When the binder died, the system wasn't finding out,
so it got into an inconsistent state and told client
apps that accessibility wasn't enabled when it actually
was.

Also fixing dumping of uiautomation, which was failing
with an NPE.

Fixes: 70338333
Fixes: 70227110
Test: Repro case in 70227110 no longer fails.
Ran a11y and UiAutomation CTS.
Ran a11y system server unit tests, and added one to verify
the new behavior.
Change-Id: I4fa6067f8316114a925de86d3fac611e6196da3e