Add additional 2 binder fuzzers

This CL aims to add an additional set of fuzzers for binder, focusing
on BufferedTextOutput and MemoryDealer.

Test: These fuzzers were tested on a Pixel 3a for a few million
      iterations without fuzzer-side crashes.
Signed-off-by: Michael Ensing <michael.ensing@leviathansecurity.com>
Change-Id: If7493ce24c78267459696a706dd67c015cf33080