Remove InterfaceState and Role @IntDef from TetheredSettings.

@InterfaceState and @Role won't be exposed as module-lib APIs from
EthernetManager after migration, which are not visible for Settings
code, remove them as well.

Bug: 210586283
Test: m Settings
Change-Id: I49f0e8401681e66d6f5853c8eb3205fcef803c25