systemui: separate proguard files into multiple ones

- Keep proguard_common still containing all of them.
- To allow customization per form factor with only inclusion of
  proguard_common_core.flags.
- Minor bp lint fix using bpfmt for SystemUIPluginLib

Flag: NONE
Test: build
Bug: 301283783
Change-Id: Idf352e7bfe542d263ad2ef4c1cda80d818ed54e6