Use ro.vendor.api_level to see the vendor API level

ro.vendor.api_level already calculated the complex api_level for
tests to use. It can replace the existing vendor api level logics.

Bug: 201727948
Test: atest vts_treble_vintf_vendor_test
Change-Id: I538506aaccc177601a3a19a8c6d051357bfd2430
2 files changed