4.20 update for org.eclipse.core.filebuffers.tests and bump to Java 11

Required for
https://git.eclipse.org/r/c/platform/eclipse.platform.text/+/179071

Moving to Java 11 as platform requires it anyhow

Change-Id: Idd4ab4e3420ff698fe74d70e3f40af9e650fb163
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.text/+/179912
Tested-by: Platform Bot <platform-bot@eclipse.org>
4 files changed