SystemServer: Sanitize build rules

Move optimization to pre-jarjar to prevent build warning
Uniformize bp in SystemServer to have common pattern
Share build flags with tests

Update proguard to allow for optimization

Bug: 288450479
Bug: 321804999
Test: mmm packages/modules/Bluetooth/service
Change-Id: I0492696b963a604029d3e38cc1ea649f704fd84d