docs: improve the Deployment Role document

[juzhiyuan]

Current State

Resource

1. Document Link: https://apisix.apache.org/docs/apisix/next/architecture-design/deployment-role/

Improvements

1. SEO: Missing keywords
2. Deployment Role: What's a Role? Should it be options or modes?
3. This document contains a table that explains what's traditional, decoupled, and standalone, but the description field misses details.
4. For the traditional's description, it's DP + CP are deployed together by default. People need to disable enable_admin manually. How about updating it to XXXX. This mode enables "enable_admin" by default?
5. This document mentions Control Plane. Some developers will get confused because of the relationship between Dashboard and AdminAPI.
6. In the Traditional section, the diagram shows Admin API is listening on the 9180 port, but our document uses :9080/apisix/admin/XXX by default. Should we use the same port? Or should we explain why we use a different port?
7. In the standalone section, we should also link readers to the Standalone document.
8. How about adding more `reasons/benefits for each mode? The readers will know why and which way is suitable for their case.
9. It's an English version only currently, need to translate to Chinese as well. cc @hf400159

Desired State

See Current State.

[guitu168]

1. We can test in different modes so that users can intuitively feel the difference between the three modes.
2. It needs to be confirmed that if this function is released in the next version, it is necessary to explain to the user whether it is possible to directly upgrade the lower version of APISIX to the new version.
3. For 4, the description is still not clear. Should be: xxx, if you want to achieve independent deployment of CP and DP, you need to disable enable_admin.
4. We need a how-to document that tells users how to deploy these three methods, rather than just giving examples of configuration files.

[kayx23]

Hi - this issue seems outdated. Please re-evaluate and see if this can be closed. Thanks.