Update DEVELOPER_GUIDE.md instructions for JDK-11

[reta]

Description

Update DEVELOPER_GUIDE.md instructions for JDK-11, fixes the annoying deprecation failure:

Executing Gradle on JVM versions 16 and lower has been deprecated. This will fail with an error in Gradle 9.0. Use JVM 17 or greater to execute Gradle. Projects can continue to use older JVM versions via toolchains. Consult the upgrading guide for further information: https://docs.gradle.org/8.10.2/userguide/upgrading_version_8.html#minimum_daemon_jvm_version


> Configure project :
=======================================
OpenSearch Build Hamster says Hello!
  Gradle Version        : 8.10.2
  OS Info               : Linux 6.11.0-9-generic (amd64)
  JDK Version           : 11 (Ubuntu JDK)
  JAVA_HOME             : /usr/lib/jvm/java-11-openjdk-amd64
  Random Testing Seed   : AE535EC00EACC589
  In FIPS 140 mode      : false
=======================================

FAILURE: Build failed with an exception.

* What went wrong:
Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0

Related Issues

N/A (popped up in Slack from community member)

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[andrross]

Lots of things out of date here. Some file references are now stale (buildSrc/version.properties). The comment about JDK 17 being the bundled JDK is wrong. Could we simplify this to say something to the effect of: "We recommend installing the latest LTS JDK and setting it as JAVA_HOME. To run the full suite of bwc tests you must also install and configure JAVA11_HOME and JAVA17_HOME."

Update: I'm not sure JDK 11 is required, but it seems JDK 17 is.
Update 2: Both JDK 11 and 17 are required for the bwc tests.

[reta]

Lots of things out of date here. Some file references are now stale (buildSrc/version.properties). The comment about JDK 17 being the bundled JDK is wrong.

It is, was focusing on immediate "need" but you are 100% right, going over the whole document

[reta]

@andrross LGTY? thanks!