Server: add PUID:PGID envs to server container

[redrathnure]

The fix of a few issue with around rootless image:

1. Fix file and dirs permissions for run with non default uid/gid user
2. add PUID and PGID to explicitly specify IDs for internal user
3. add possibility to specify custom user:group (-u uid:gid arg)
4. split data from data/dynamic_created_content from source code

[laurent22]

Thanks for your recent pull requests, I appreciate the quality work however I'm not sure this is the direction we want for Joplin Server. One issue unfortunately is that we also use all this for Joplin Cloud and I'm scared that one unexpected bug will get in and break the service for a lot of people. Another thing is that if one day I need to build Joplin Cloud and I can't due to some issue with the Docker config, I'm not sure I'll be able to fix it in a timely manner since I'm not familiar with this new code.

Not saying I strictly want no changes on Joplin Server but there are more constraints than for the rest of the project. I will still review your pull requests into more details and let you know what we can do, but I thought I'd give you a head up.

One change that I would accept, which I think is related to your dockerx PR, is the ability to build the ARM64 version along the existing AMD64 (as is done here).

[redrathnure]

@laurent22 OK, I see. Just let me know if you need any kind of adjustments or explanations here.