healthd: create SEPolicy for 'charger' and reduce healthd's scope

healthd is being split into 'charger' and 'healthd' processes, that
will never run together. 'charger' is to be run only in charge-only
and recovery, while healthd runs with Android.

While they both share much of battery monitoring code, they both now
have reduced scope. E.g. 'charger', doesn't need to use binder anymore
and healthd doesn't need to do charging ui animation. So, amend the
SEPolicy for healthd to reduce it's scope and add a new one for charger.

Test: Tested all modes {recovery, charger-only, android} with new policy

Change-Id: If7f81875c605f7f07da4d23a313f308b9dde9ce8
Signed-off-by: Sandeep Patil <sspatil@google.com>