Clarify the JDK requirement in Developer Guide

[tlfeng]

Is your feature request related to a problem? Please describe.
The description about JDK requirement for OpenSearch in the Developer Guide is a bit confusing:
https://github.com/opensearch-project/OpenSearch/blob/88f17b1822beb954bda1342b896d315b8e4d2b41/DEVELOPER_GUIDE.md#jdk-11

Which versions of JDK are supported to build and run OpenSearch is not quite clear.
Which test requires JAVA8_HOME, JAVA9_HOME, etc. is not mentioned.

Describe the solution you'd like
Provide a clear and concise description of the JDK requirement to build and run OpenSearch, as well as the required JAVA_HOME environment variables.

Describe alternatives you've considered
n/a

Additional context
OpenSearch documentation regarding JVM compatibility
https://opensearch.org/docs/opensearch/install/compatibility/#operating-system-and-jvm-compatibility

Support Matrix for Elasticsearch and JVM
https://www.elastic.co/support/matrix#matrix_jvm

[tlfeng]

Close the issue since the change has been merged in main and 1.x branches.