DOCS-33261: Add note that Java SDK is in Maintenance Mode (#3061)

## Pull Request Info

Indicate to users that the Java SDK is in a best-effort maintenance mode
and no longer receiving any new features.

And, per [Slack
convo](https://mongodb.slack.com/archives/CL9JSLTGE/p1698666451443479),
confirm you can use other SDKs in a Java project.

### Jira

- https://jira.mongodb.org/browse/DOCSP-33261

### Staged Changes

- [Java SDK
landing](https://preview-mongodbcbullinger.gatsbyjs.io/realm/docsp-33261-java-sdk-guidance/sdk/java/)
- [Install - Java
SDK](https://preview-mongodbcbullinger.gatsbyjs.io/realm/docsp-33261-java-sdk-guidance/sdk/java/install/)

### Reminder Checklist

If your PR modifies the docs, you might need to also update some
corresponding
pages. Check if completed or N/A.

- [x] Create Jira ticket for corresponding docs-app-services update(s),
if any
- [x] Checked/updated Admin API
- [x] Checked/updated CLI reference

### Review Guidelines


[REVIEWING.md](https://github.com/mongodb/docs-realm/blob/master/REVIEWING.md)

source/includes/note-java-maintenance-mode.rst

@@ -0,0 +1,8 @@
+.. note:: Java SDK in Maintenance Mode
+
+   The Java SDK is in best-effort maintenance mode and **no longer receives 
+   new development or non-critical bug fixes**. To develop your app with new 
+   features, use the :ref:`Kotlin SDK <kotlin-intro>`. You can use the Java SDK 
+   with the Kotlin SDK in the same project. 
+
+   Learn more about how to :ref:`<kotlin-migrate-from-java-sdk-to-kotlin-sdk>`. 

source/sdk/java.txt

@@ -38,10 +38,21 @@ Realm Java SDK
    :depth: 2
    :class: singlecol
 
+
 Use the Realm Java SDK to develop Android apps in Java or Kotlin. To develop
 multiplatform apps using Kotlin Multiplatform (KMP), refer to the
 :ref:`Realm Kotlin SDK <kotlin-intro>`.
 
+SDK in Maintenance Mode
+-----------------------
+
+This SDK is in best-effort maintenance mode and **no longer receives 
+new development or non-critical bug fixes**. To develop your app with new 
+features, use the :ref:`Kotlin SDK <kotlin-intro>`. You can use the Java SDK 
+with the Kotlin SDK.
+
+Learn more about how to :ref:`<kotlin-migrate-from-java-sdk-to-kotlin-sdk>`. 
+
 .. kicker:: What You Can Do
 
 Develop Apps with Realm

source/sdk/java/install.txt

@@ -10,12 +10,20 @@ Install Realm - Java SDK
    :depth: 2
    :class: singlecol
 
+.. include:: /includes/note-java-maintenance-mode.rst 
+
 Overview
 --------
 
-This page details how to install Realm in your project
+This page details how to install Realm using the Java SDK in your project
 and get started.
 
+You can use multiple SDKs in your project. Because the Java SDK is no longer
+receiving new development, this is useful if you want to 
+use new features in your app. For example, you can add Atlas 
+Device Sync's :ref:`Data Ingest <optimize-data-ingest>` feature to your 
+app using the Kotlin SDK while continuing to use Java for everything else.  
+
 Prerequisites
 -------------