Today, MallocLimit will end the VM with a fatal error if the malloc limit is reached.

For regression- and stability tests it would be useful to use `-XX:MallocLimit` to inject native OOMs (cause malloc to return NULL).

This is also the prerequisite to get rid of the `MallocMaxTestWords` machinery (see https://bugs.openjdk.org/browse/JDK-8293292) by replacing it with MallocLimit.