Add an additional layer of inheritance for `aosp_ripcurrent` and
`aosp_ripcurrent`.
This change adds a common layer of inheritance(ripcurrent_generic.mk)
for non-factory products. This makes it easier to configure factory
and non-factory products differently.
non-factory `ripcurrent` products now inherits from
`device/google/shusky/ripcurrent_generic.mk` which inherit from
`device/google/shusky/device-ripcurrent.mk`.
aconfig flags: Flag: EXEMPT mechanical refactoring
build flags: Flag: EXEMPT mechanical refactoring
Bug: 332219400
Bug: 335564645
Test: lunch factory_ripcurrent-trunk_staging-userdebug && m
lunch aosp_ripcurrent-trunk_staging-userdebug && m
lunch aosp_ripcurrent_fullmte-trunk_staging-userdebug && m
Change-Id: Ieb552a075e35215cb027b6d5a91d84168d9e6a45
