Raise minimum required Java version to 11

[kwin]

As ACS AEM Commons only supports AEM 6.5.(10) and AEM as a Cloud Service and the former optionally runs on Java 11 while the latter runs by default on Java 11 I think we should drop support for Java 8.

That allows to leverage new language features like Streams, Http Client (#3276) and probably reduce the usage of thirdparty libraries like Google Guava.

[kwin]

@davidjgonzalez and @YegorKozlov WDYT?

[YegorKozlov]

@davidjgonzalez and @YegorKozlov WDYT?

Requiring Java 11 is fine to me, especially if it helps to make the code leaner and cleaner. Conservative users running on JDK 1.8 will need to either upgrade JDK or use older releases.

There can be many reasons why people are still on JDK 1.8, like legacy code that require java.xml.ws, java.activation or whatever else was removed in JDK 11, but none of these is a reason why we should support JDK 1.8.
It's been two years since 1.8's EOL and it's time to upgrade.

[davidjgonzalez]

Fine with me as well. There have been many years for users to switch to later versions of Java.

This would bump us to 7.0.0