expose docker caching from host to the VM

[amiller]

It's too bad starting a dstack guest vm instance is so slow, even when the application containers mostly consist of frequently-reused containers. It would be great if the guest could use the host as an (untrusted) local cache.

Here's relevant docs on how to configure container drivers (should be applicable to podman) registries to point elsewhere (i.e. to a service on the host)
https://github.com/containers/image/blob/main/docs/containers-registries.conf.5.md#remapping-and-mirroring-registries

excuse the brief design issue :]

[kvinwang]

Docker seems to not support /etc/containers/registries.conf.
Teepod already supports configuring mirror registry here:

dstack/teepod/teepod.toml

Line 23 in a5edadf

docker_registry = ""

The local cache can be set up according to the official doc
However, only official docker hub registry is supported for mirroring.