use robust connection for http requests

[floriankrb]

We should be more robust to temporary failure of a web server. This function implements a policy of raising exception or retrying depending on the error code from the server. It could be added to anemoi-registry.

https://github.com/ecmwf/multiurl/blob/c4de5fca3e86a924e3024c737ea051f0d288df40/multiurl/http.py#L463