RFR (XS): 8218672: AOT code root scanning shows in the wrong position in the logs

[Thomas Schatzl]

Hi all,

  can I have reviews for this small change that fixes the position of
the "AOT Code Root Scan" phase, moving it to appear under the "Ext Root
Scan" phase where it is handled in?

CR:
https://bugs.openjdk.java.net/browse/JDK-8218672
Webrev:
http://cr.openjdk.java.net/~tschatzl/8218672/webrev/
Testing:
hs-tier5 (there is some jfr test case that complains if the phase names
were messed up)

Thanks,
  Thomas