Make images leaner using various techniques

[dhruvkb]

In the beginning we used Alpine images for as many containers as possible. But over time, as we added new features like fancy prompts and healthchecks, we have altogether abandoned Alpine Linux as well as thrown any concern for image sizes out the window.

The mission is to make all images leaner, by using multi-stage builds, extending from Alpine images (or smaller) and reducing the number of layers as much as possible and other techniques not mentioned here, if any.