libbinder: Do not destruct TextOutput

Recent changes meant that a log is more likely during process shutdown,
given certain races w/ alog. However, this should have still been
possible before. Allocating TextOutput objects on the heap to avoid them
getting destructed.

Fixes: 149516130
Test: while ! cmd activity get-current-user 2>&1 | grep FORTIFY; do :; done
Change-Id: Ie5c066172203172a80c135ad5aa7da09b362ee73