Update insert method for battery database

1. Add conflict code to ignore the confliction and return -1 when
insert fails.
2. Add boolean return value to show whether insert sucessfully
3. Add unit test. We don't write robo test because robolectirc use
"update" to shadow "insert" operation, which returns the wrong data.

Bug: 77968649
Test: SettingsUnitTest
Change-Id: Ibd3b53cdb1796d74ea4a2ca1f067e2b302b939e9