Update installation and usage instructions from Java 11 to Java 17

[kmartens27]

Describe your use-case which is not covered by existing documentation.

Since Java 17 is fully supported by Jenkins, the documentation needs to transition from using Java 11 as the preferred version, to using Java 17.

This includes areas such as installation and usage documentation, where Java 11 is used.

Java 17 provides more functionality, is faster, and provides more overall tools & support for development.

It may also need to be made clear that we are not dropping support for Java 11. We are only transitioning to use Java 17 because it is a more updated and useful version. Java 11 support will continue in Jenkins. Making this transition will help users upgrade and migrate properly, while making sure that the benefits to this are understood.

This was inspired by the Debian 12 release, as this will not be delivered with JDK11.

Reference any relevant documentation, other materials or issues/pull requests that can be used for inspiration.

Pages that may need updates include:

• [x] https://www.jenkins.io/doc/administration/requirements/java/
• [x] https://www.jenkins.io/doc/book/installing/linux/
• [ ] https://www.jenkins.io/doc/book/installing/windows/
• [x] https://www.jenkins.io/doc/book/installing/initial-settings/
• [x] https://www.jenkins.io/doc/book/installing/docker/
• [x] https://www.jenkins.io/doc/book/pipeline/docker/
• [x] https://www.jenkins.io/doc/book/pipeline/syntax/

Needed additional documentation

• [x] instructions on upgrading Jenkins'/JVM from Java 11 --> Java 17 (https://github.com/jenkins-infra/jenkins.io/pull/6543)

[kmartens27]

The java upgrade guidelines currently describe upgrading from Java 8 to 11. Since there is still a user base on Java 8, and external links that navigate to this page, it should remain as is (but will have a note inserted at the top of the page to direct users to a new page for the upgrade from 11 to 17). The Java 11 to 17 upgrade instructions will have their own separate page, but most of the steps carry over.

The java requirements will have a new section added above the "Running Jenkins on Java 11 in Docker" section titled "Running Jenkins on Java 17 in Docker). This will retain the current information, but inform users that 17 would be a better option.