[Enhancement] kcl doc gen: optimize the document format and styles

[amyXia1994]

Enhancement

parent issue: #139

This issue is raised according to catalog doc sync PR:

https://kusionstack.io/docs/reference/model/catalog_models/internal/container/doc_container

The model docs on the official website have been manually modified and are more more clear and human-friendly than the documents generated directly by the kcl-doc tool.

The doc gen spec and templates should be optimized accordingly.

cc @ffforest

• [Enhancement]support an option to display schema attributes in a flatten way #164
• [Enhancement] doc tool generate provides referenced by information on schema #165
• [Enhancement] doc generate tool: clearer distinction between attributes in the generated docs #166