Export OpenAPI definitions from service examples; affects [dynamic endpoint static] (#8966)

* WIP export OpenAPI definitions from service examples

* allow services to optionally define an OpenApi Paths Object instead of examples

* make use of param descriptions and required query params

* convert other 'core' services to declare openApi..

..instead of examples

* tweak descriptions for standard query params

* move stuff around, add a high-level integration test for category2openapi

* update simple-icons text refs #9054

* remove legacy param names