Add a fuzzer for libpdx ServiceDispatcher class.

Adds a fuzzer for the libpdx ServiceDispatcher class.
Test: Ran fuzzers for a couple million iterations on a Pixel3a device. This ran at about 600 executions per second,
resulting in 2% coverage for the entire memory space, however we believe it is a much higher percentage of libpdx coverage
alone.

Signed-off-by: Corbin Souffrant <corbin.souffrant@leviathansecurity.com>
Change-Id: Ie5d7ea76d182843e15dcaca4639c54656652a238