libbinder - split out libbatterystats_aidl

Moving this out of libbinder saves 4KB in 44 processes (on cuttlefish) =
176KB of private dirty memory (that is, this takes libbinder from 84 to
80 KB of private dirty memory). This also adds the cost of a new library
in 6 processes (6 * 12KB = 82 KB of additional private dirty memory).

Future considerations: once all these interfaces are moved, I'll file
bugs to have corresponding teams convert them to AIDL.

Bug: 183654927
Test: boot
Change-Id: Ic48f0ac8d5ebd27c76774f680b1891afcb1fa4c1