Programmatic way to get available training/inference containers.

**Describe the feature you'd like**
It would be very helpful to be able to programmatically get all available framerworks, py versions etc, prior to `sagemaker.image_uris.retrieve(...)`.
This would allow people to see what containers are available, without having to dig through repositories and try to find supported images or continuously hit errors until the right permutation of framework, framework version, and py version are achieved.

**How would this feature be used? Please describe.**
Something like `sagemaker.image_uris.show_images()` or something like that would be desired. This ideally would take no parameters and show maybe a dictionary of all the frameworks, framework versions, and respective py verisons.

**Describe alternatives you've considered**
Considering programmatically parsing: https://github.com/aws/deep-learning-containers/blob/master/available_images.md

But this does not feel like a good solution at all.

Commencez par lire le point d’entrée sagemaker.image_uris.retrieve(...) et comparez ses combinaisons prises en charge de framework, de version du framework et de version de Python avec deep-learning-containers/available_images.md. Définissez comment une API sans paramètre de type show_images() devrait représenter toutes les combinaisons disponibles, et déterminez comment vérifier l’exhaustivité par rapport aux conteneurs répertoriés sans nécessiter de nouvelles tentatives de récupération ayant échoué.

Rédigé par le modèle d'indexation à partir du texte de l'issue.