Migrate to IndentingPrintWriter.

Switch from using PrintWriter with manual indents to
IndentingPrintWriter to simplify and standardize the dumping code.

Bug: 79580230
Test: verify dump output looks correct
Test: atest com.android.server.power.batterysaver.BatterySaverPolicyTest
Test: atest com.android.server.power.batterysaver.BatterySaverStateMachineTest
Test: atest com.android.server.power.batterysaver.BatterySavingStatsTest
Test: atest CtsBatterySavingTestCases
Change-Id: I3ec2e4df63739fce3bb850100874b087e65c20a7