[res] Better native pointer tracking in Java

Make sure we clear the native pointers when freeing them,
so any race condition that calls into it gets a null instead
of calling into already freed object

Bug: 197260547
Test: build + unit tests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:7c2f195cfc8c02403d61a394213398d13584a5de)
Merged-In: I817dc2f5ef24e1fafeba3ce4c1c440abe70ad3ed
Change-Id: I817dc2f5ef24e1fafeba3ce4c1c440abe70ad3ed