Ensure that debug builds crash again if there is a BinderProxy leak.

This fails when trying to run the AOSP mailer with CRASH_AT_SIZE = 500,
when the check interval is reduced sufficiently so that the test is
actually executed. System server has been observed to use more than
1000 BinderProxies. Thus 5000 seems like roughly the lowest safe limit.

Note that the test is executed somewhat rarely, so we may exceed
this number by quite a few before we actually crash.

Bug: 65760710
Test: Builds, AOSP boots & works for a few tasks. Fails as expected
with reduced limit.

Change-Id: I1c999b85e1ba1bd1d166a9ffba4f0b3992ffee45