Delay fs-verity setup further after dexopt

The previous change has reduced the install time regression for about
50%-ish. Since the other code in this function, e.g. dexopt, still
access the APK, delaying fs-verity setup further avoids
evict-page-cache-then-read-back in the touched method.

Bug: 259179666
Test: atest ChecksumsTest ApkVerityTest
Change-Id: I1ab78fc201a7258b495069a52552db0d7b37b0a5