[pm] Skip parsing abis from the apex file in scan flow

From U, We merged the APK and APEX scan flows so that they run the
same code branch, rather than having ApexManager maintain a separate
parsing implementation. For parsing the abis in scan flow, because
the native libs of an Apex is located in apex_payload.img, don't need
to parse it from the original apex file when scanning the apex file.

Test: atest ScanTests#scanFirstBoot_apexDontDeriveAbis
          --iterations 100
Test: atest ScanTests --iterations 100
Test: Manual. run atest BootTest, verified the logs
Bug: 288167712
Change-Id: I3bd0d8250fd27e1aff2a16bef1495f1c9cfba472