Add Workflow Streams docs for the Java SDK

Mirrors the Python, TypeScript, and Go feature guides, sourced from the
temporal-workflowstreams contrib module (sdk-java v1.37.0) and samples-java.
Includes the Java-specific non-blocking listener subscriber API alongside
the blocking iterator, and wires the page into the sidebar, Java index
pages, and encyclopedia cross-links.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: 2 people

docs/develop/java/index.mdx

@@ -46,6 +46,7 @@ From there, you can dive deeper into any of the Temporal primitives to start bui
 - [Timers](/develop/java/workflows/timers)
 - [Side effects](/develop/java/workflows/side-effects)
 - [Versioning](/develop/java/workflows/versioning)
+- [Workflow Streams](/develop/java/workflows/workflow-streams)
 
 ## [Activities](/develop/java/activities)
 

docs/develop/java/workflows/index.mdx

@@ -31,3 +31,4 @@ import * as Components from '@site/src/components';
 - [Timers](/develop/java/workflows/timers)
 - [Side effects](/develop/java/workflows/side-effects)
 - [Versioning](/develop/java/workflows/versioning)
+- [Workflow Streams](/develop/java/workflows/workflow-streams)