Preopt system server jars with updatable bootclasspath.

Previously, we preopt system server jars without updatable bootclasspath
in the build system so that the artifacts can keep valid after a
mainline update. Things have been changed after then. We now re-compile
system server jars on the user's device after a mainline update
(b/189467174), so we no longer need the artifacts generated at build
time to keep valid. Therefore, we can preopt system server jars with
updatable bootclasspath to achieve better performance.

Bug: 199573699
Test: m services
Test: manual - 1. Build a system image and flash it into a device.
  2. adb root && adb shell grep "services" /proc/`adb shell pidof system_server`/maps
  3. See "/system/framework/oat/x86_64/services.{odex,vdex,art} in the
  output.
  4. adb logcat -d odrefresh:D odsign:D "*:S"
  5. See "odrefresh said artifacts are VALID" and no dex2oat invocation
  in the output.

Change-Id: I9c94a54aa15c46708067f4bc89ff05bc7af32a7b