Allow filter calls with a list as a pattern

This commit doesn't attempt to replace the filter
calls with anything more idomatic for now.

It also removes the case for filter-out, because
the actual function name is filter_out and wasn't
being used anyways. Even if I were to change it
to filter_out, that would produce buggy results:

ifneq (,$(filter $(TARGET_BUILD_VARIANT), userdebug eng))
endif
ifneq (,$(filter-out $(TARGET_BUILD_VARIANT), userdebug eng))
endif

Both of these would produce:

if g["TARGET_BUILD_VARIANT"] in ["userdebug", "eng"]:
  pass

Fixes: 218702402
Test: go test
Change-Id: I566079e5d3a364c42db14045aa1bab9d99eba05f