Don't allocate GlobalRefs for BinderProxy

This removes all GlobalRef allocation as part of building BinderProxys.
Previously these were used to map IBinders to the corresponding
Java object, so the Java objects could be reused. We now keep
that mapping at the Java level.

This means we often need to call into Java to look up or allocate
a BinderProxy. But this replaces a prior call to Java to dereference
a WeakReference. The Java custom Java map-to-WeakReference data
structure is probably not terribly efficient, but the original
attachement mechanism did not seem to be either. And this
avoids potentially even more catastrophic issues when the number
of GlobalRefs approaches its limit.

We decrease GC triggering frequency from 200 to 1000 allocated
references. This now only applies to other kinds of JNI References
allocated by Binder.

I saw a maximum bucket size of 16 for the ProxyMap data structure
while briefly exercising a freshly booted device. That occurred
in system_server.

Bug: 65760710

Test: Built and booted master with some debugging output. Looks sane.
Change-Id: I322c4d8e9c8e198586d591580c2cdbb094906677