feat: docker images provider

[aarnphm]

Is your feature request related to a problem? Please describe.

It would be nice if bentoml provided a Pythonic way of using docker_base_image with bentoml/model-server.

Describe the solution you'd like

@env(docker_base_image=bentoml.docker.ProvidedImages(os="debian", gpu=True, python_version=3.7))
class Service(bentoml.Service)

It should also have backward compatibility so that users can have a better experience when new releases is introduced on docker

Exploration ideas:

• ProvidedImages would store a list of images provided by BentoML under $BENTOML_HOME and could implement a caching options so that it wouldn't slow down BentoService
• Or an easier way is that this class only converted the given options to the correct string syntax with bentoml docker releases and then utilize the the current behaviour or docker_base_image.

[aarnphm]

This is also related to current redesigning package bundle, thus will be on hold at the moment.