refactor(docs): simplify docs files / pipelines (#9633)

* refactor(doc): only use one command

* restructure

* move all generated helpers to a dedicated directory

* move to pathlib

* and more pathlib

* add empty generated folder

readthedocs.yml

@@ -14,9 +14,6 @@ build:
     python: "3.9"
   jobs:
     post_install:
-      - echo "Generating API schema file"
       - pip install -U invoke
-      - invoke migrate
-      - invoke int.export-definitions --basedir "docs"
-      - invoke dev.schema --filename docs/schema.yml --ignore-warnings
-      - python docs/extract_schema.py docs/schema.yml
+      - echo "Generating API schema file"
+      - invoke build-docs