[Pod] Only include the relevant javacflags in SysUI build rules.

Now that SystemUI-application has existed for long enough that it's
stable, we can start pruning SystemUI/Android.bp to have
SystemUI-application and SystemUI-core include just things they truly
need.

Fixes: 430627653
Bug: 307607958
Flag: EXEMPT build change
Test: m SystemUI-application
Change-Id: Ia22b7d79bad25ad6d5eef0840c063e4c6afb154e