Recoverable GWP-ASan: Don't tell ActivityManager

Currently, debuggerd tells the teacher that an app that received a fatal
signal. On the playground, dobbing on a process that doesn't actually
need to be killed is considered a friendship-ending move.

Because recoverable GWP-ASan is *supposed* to not crash your app,
suppress this behaviour and don't let ActivityManager know about the
crash.

Bug: N/A
Test: Run a use-after-free in an app that's using recoverable GWP-ASan,
through the 'libc.debug.gwp_asan.recoverable.<app_name>=1' and
'libc.debug.gwp_asan.process_sampling.<app_name>=1' sysprops.

Change-Id: I033ea67d577573df10936e37db7302d4f4bc0069