Implemented native functions and types for blastula management.

This patch adds native support for spawning and managing blastula pools,
as well as several code cleanups and modernizations.

Changes includes:
* A function to fork blastulas
* A table for managing blastula-related data
* Functions for adding and removing blastula data from the
aforementioned table
* Switching from NULL to nullptr
* Replacing string-passing error handling with a curried failure
function
* Utility functions for handling managed objects
* JNI functions for blastula pool management

Change-Id: I12cd9f2c87a2e3c00d64b683edf3631e29a51551
Topic: zygot-prefork
Test: make & flash & launch apps & check log for messages
Bug: 68253328