Sandbox: updates for the main branch/release

In this commit, main changes are included:

- Add the standard Apache license headers for files
- Refactor the Dockerfile.*.rockylinux 9
- Adopt a more friendly way to support running the sandbox with
  multi-nodes.
- Strengthen the robustness of sandbox.

Author: tuhaihe

README.md

@@ -68,9 +68,8 @@ Linux OS (including RHEL/Rocky Linux, and Ubuntu) and macOS.
 ### Try out quickly
 
 Welcome to try out Cloudberry via building [one Docker-based
-Sandbox](https://github.com/apache/cloudberry-bootcamp), which is tailored to
-help you gain a basic understanding of Cloudberry's capabilities and features
-a range of materials, including tutorials, sample code, and crash courses.
+Sandbox](./devops/sandbox), which is tailored to help you gain a basic
+understanding of Cloudberry's capabilities and features.
 
 ## Repositories
 
@@ -79,10 +78,8 @@ this, there are several ecosystem repositories for Cloudberry, including the
 website, extensions, connectors, adapters, and other utilities.
 
 * [apache/cloudberry-site](https://github.com/apache/cloudberry-site): website and documentation sources.
-* [apache/cloudberry-bootcamp](https://github.com/apache/cloudberry-bootcamp): help you quickly try out Cloudberry via one Docker-based Sandbox.
-* [apache/cloudberry-gpbackup](https://github.com/apache/cloudberry-gpbackup): backup utility for Cloudberry.
+* [apache/cloudberry-backup](https://github.com/apache/cloudberry-backup): backup utility for Cloudberry.
 * [apache/cloudberry-go-libs](https://github.com/apache/cloudberry-go-libs): go-libs for Cloudberry.
-* [apache/cloudberry-gpbackup-s3-plugin](https://github.com/apache/cloudberry-gpbackup-s3-plugin): S3 plugin for use with Cloudberry backup utility.
 * [apache/cloudberry-pxf](https://github.com/apache/cloudberry-pxf): Platform Extension Framework (PXF) for Cloudberry.
 
 ## Community & Support

devops/sandbox/.env

@@ -1,2 +1,21 @@
-CODEBASE_VERSION=1.6.0
+# --------------------------------------------------------------------
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements. See the NOTICE file distributed
+# with this work for additional information regarding copyright
+# ownership. The ASF licenses this file to You under the Apache
+# License, Version 2.0 (the "License"); you may not use this file
+# except in compliance with the License. You may obtain a copy of the
+# License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied. See the License for the specific language governing
+# permissions and limitations under the License.
+#
+# --------------------------------------------------------------------
+CODEBASE_VERSION=2.0.0
 OS_VERSION=rockylinux9