Move management `ErrorPage` registration from the `WebMvcEndpointChildContextConfiguration` to `WebMvcEndpointChildContextConfiguration` and only add it when the error controller is registered. Fixes gh-17938
Move management `ErrorPage` registration from the `WebMvcEndpointChildContextConfiguration` to `WebMvcEndpointChildContextConfiguration` and only add it when the error controller is registered. Fixes gh-17938