revise the original wordpress example with Alicloud RDS as database backend

[liu-hm19]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• [x] N
• [ ] Y

2. What is the scope of this PR (e.g. component or file name):

This PR modifies the files in konfig/appops/wordpress

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• [ ] Affects user behaviors
• [ ] Contains syntax changes
• [ ] Contains variable changes
• [ ] Contains experimental features
• [ ] Performance regression: Consumes more CPU
• [ ] Performance regression: Consumes more Memory
• [x] Other

This PR revises the original wordpress example with hybrid resources from Kubernetes + Alicloud OSS to Kubernetes + Alicloud RDS, using the Alicloud RDS as the database backend.

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• [ ] N
• [x] Y

This PR changes the original wordpress example. Alicloud OSS seems not fitting well with the original demo, thus we decided to use Alicloud RDS for better demonstration.

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• [ ] Unit test
• [ ] Integration test
• [ ] Benchmark (add benchmark stats below)
• [x] Manual test (add detailed scripts or steps below)
• [ ] Other

As shown in konfig/appops/wordpress/README.md, executing kusion apply --yes can successfully apply the Alicloud and Kubernetes resources.

6. Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None