Split ALL_MODULES.*.REQUIRED and friends between target/host

So that we actually respect different LOCAL_REQUIRED_MODULES for the
host and device versions instead of unioning them. That got particularly
problematic when LOCAL_SHARED_LIBRARIES is implicitly added to
LOCAL_REQUIRED_MODULES. We also used to walk through device-only modules
when filling out the list of required modules, which triggered even more
extra installations.

This also changes the requirements for PRODUCT_HOST_PACKAGES so that it
no longer accepts target-only phony modules (since we can now
differentiate them). They were all removed in previous patches.

Test: treehugger; diff resulting builds
Test: diff list of product_target_FILES and product_host_FILES
Change-Id: I2ed8950320d31f5693323ad8cef6ec5b6780b7d4