ANDROID: GKI: power_supply: add batt_age_level property

Add batt_age_level property to support loading multiple profiles
based on the battery age level specified by the user.

Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>
(cherry picked from commit 0fe2e0aadcff78083a7f85f74c6e931a7c74dcc1)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 150789066
Change-Id: I41e61c615f2d1df988a0de83e4e2dbddd7a36441