build: attach sources and javadoc jars to release builds

[marevol]

Summary

Release builds did not generate sources and javadoc jars because maven-source-plugin was missing and maven-javadoc-plugin had no jar goal execution. The super POM release-profile that used to handle this is no longer available in current Maven versions, so publishing to Maven Central fails validation during mvn release:perform.

Changes Made

• Add maven-source-plugin 3.3.1 with an attach-sources execution (jar-no-fork goal)
• Add an attach-javadocs execution (jar goal) to the existing maven-javadoc-plugin

Testing

• Ran mvn package -DskipTests and confirmed that both *-sources.jar and *-javadoc.jar are generated under target/

Additional Notes

• Same fix as build: attach sources and javadoc jars to release builds opensearch-runner#20 (codelibs/opensearch-runner@25c54af)