Render OpenAPI Spec of Admin APIs and Control APIs

## Description

So far, the APISIX Admin APIs and Control APIs are hosted at https://apisix.apache.org/docs/apisix/admin-api/ using Markdown. To enhance the experience, an OpenAPI Spec render page would be much better.

Note: This change applies starting with APISIX v3.13; previous versions will continue to use the markdown format.

## TODO

- [ ] Which OpenAPI Render Library to use?
- [ ] Build & Upload OpenAPI Spec files to `apache/apisix` repo.
- [ ] Delete Markdown contents. (Admin API and Control API)
- [ ] Use OpenAPI Render Library to render specs.

Start with the Admin API and Control API documentation at https://apisix.apache.org/docs/apisix/admin-api/ and identify the existing Markdown content and the OpenAPI specification files in the apache/apisix repository. Research and choose an OpenAPI render library, then define how specs will be built and uploaded for APISIX v3.13. Done means the Markdown content is replaced by rendered specs while previous versions retain Markdown.

Written by the indexing model from the issue text.