Enhance ShardingSphere Operator

# Apache ShardingSphere

Apache ShardingSphere is positioned as a Database Plus, and aims at building a standard layer and ecosystem above heterogeneous databases. It focuses on how to reuse existing databases and their respective upper layer, rather than creating a new database. The goal is to minimize or eliminate the challenges caused by underlying databases fragmentation.

Page: https://shardingsphere.apache.org/
Github: https://github.com/apache/shardingsphere 

# Background

ShardingSphere on Cloud has released several versions of ShardingSphere Operator. It supports three different CRDs. Now, we want to enhance this operator with following issues:

- #277
- #272
- #270
- #254

# Task

Please check in different issues for more details of tasks.
 
# Relevant Skills

1. Master Go language, Ginkgo test framework
2. Have a basic understanding of Apache ShardingSphere Concepts
3. Be familiar with Kubernetes Operator, kubebuilder framework

# Targets files

Controllers - https://github.com/apache/shardingsphere-on-cloud/blob/main/shardingsphere-operator/pkg/controllers

Review issues #277, #272, #270, and #254 for the concrete operator tasks before changing anything. Start in shardingsphere-operator/pkg/controllers and use the Go, Ginkgo, Kubernetes Operator, and kubebuilder context described in the issue; done means the selected enhancement is implemented and its relevant tests pass.

Written by the indexing model from the issue text.