Persist $HOME contents and move init to dockerfile

[axonasif]

gitpod-io/gitpod#19615

[complyue]

Thanks @axonasif !

It works pretty well after some tweaks now.

I wonder if axonasif/workspace-base is finding ways to gitpod/workspace-base? If that's the case I don't mind wait a while for the merge there, then incorporate the more "official" base image.

[axonasif]

@complyue, it was proposed but I don't see any traction at the moment.
I've mentioned this in the dockerfile comments, here's the relevant issue: gitpod-io/workspace-images#1071

[complyue]

Okay, I'm merging for now, then. Thanks again @axonasif !