reduce docker image size

[LTS42]

Dockerfile was not efficient.
This makes it smaller.
Tested to see the result is the same.

With original dockerfile, it would take about 600 seconds on M2.
With the new dockerfile, it takes about 70 seconds.

[sb2nov]

Thanks -- It conflicts with your other PR - could you resolve the conflict?

[1993CRV]

@LTS42 @sb2nov thoughts on using Alpine instead of Debian and Ubuntu? it's only 5 MB

https://hub.docker.com/_/alpine

Comparison:

Image	Compressed Size (MB)
Ubuntu Xenial 16.04	44.35
Ubuntu Noble 24.04	27.53
Debian Stable Slim	27.8
Alpine	3.45

[sb2nov]

I'm supportive - do you want to send a PR ?

[LTS42]

@LTS42 @sb2nov thoughts on using Alpine instead of Debian and Ubuntu? it's only 5 MB

https://hub.docker.com/_/alpine

alpine will end up taking more time because of how bare bone it is (I tried).
by using debian:stable-slim, we are effectively offloading essential build time to download time which in most cases will be faster.
if you are able to come up with a branch, I can test it on my machine how long it takes (or you can, with this branch and your new branch).
for now, I'm resolving and merging (with approval)

[sb2nov]

Merged this and we can try to move to alpine in a followup if we make it work but this is already way better