Introduces new heap-zero-init API. We've realised that it's better to be
able to individually control MTE and heap zero-init. Having
heap-zero-init not be controllable without affecting MTE affects our
ability to turn off heap-zero-init in zygote-forked applications.
Bug: 135772972
Test: On FVP: atest -s localhost:5555 malloc#zero_init \
Test: malloc#disable_mte heap_tagging_level
Change-Id: I8c6722502733259934c699f4f1269eaf1641a09f
Mitch Phillips