RFR: 8213569: Bump minimum boot jdk to JDK 11

[Tim Bell]

Mikael:

> Please review this change which bumps the minimum boot jdk to JDK 11 (see [1] for Boot-JDK policy).
>
> bug:https://bugs.openjdk.java.net/browse/JDK-8213569  <https://bugs.openjdk.java.net/browse/JDK-8213569>
> webrev:http://cr.openjdk.java.net/~mikael/webrevs/8213569/webrev.00/open/webrev/  <http://cr.openjdk.java.net/~mikael/webrevs/8213569/webrev.00/open/webrev/>

Looks good.  Test builds are running in good shape.

Tim