libbatteryservice: remove binder details

libbatteryservice_headers only contains struct defs now. This
minimizes headers that are not intended for vendors to use.
Bug: 68724651
Test: builds

Change-Id: If4a9d897c79958de1a114321a7340fe94866bf04
Merged-In: If4a9d897c79958de1a114321a7340fe94866bf04
(cherry picked from commit 09428906)