Show file path when listing APEXes (1/n)

-f now works for APEXes as well.

Bug: 140813980
Test: adb shell pm list packages --apex-only -f
package:/system/apex/com.android.apex.cts.shim.apex=com.android.apex.cts.shim
package:/system/apex/com.android.art.debug.apex=com.android.art
package:/system/apex/com.android.conscrypt.apex=com.google.android.conscrypt

Change-Id: I6206c4db392a37152f14aa5510c35e52f565f9a6