When using MSAN, mjData->buffer is marked as poisoned, despite being initialized with zeroes.
This is useful for catching computations that accidentally use uninitialized values.
However, when using engine_print, it's OK to assume the buffer is initialized to zeros.
PiperOrigin-RevId: 456085776
Change-Id: I9d85e37fa82958eb54ac413140543a6581aa46ad