adbd: add source/sink services.

Add some services that skip the service fd to see how much of a benefit
it'll be to eliminate it.

Test: adb raw source:$((300 * 1024 * 1024)) | pv > /dev/null
Test: dd if=/dev/zero bs=1M count=100 | pv | adb raw sink:$((100 * 1024 * 1024))
Change-Id: I042f25f85b16ae9869cb1f1e306d8671b024ed97