Tidy up Dockerfiles and remove dependency on drone/ca-certs

[UnlimitedCookies]

I would love to test out the UI rewrite, but I am confused by the seemingly duplicate Dockerfiles.

E. g. Dockerfile.agent{.alpine} seem quite similar.

The Dockerfile.agent apparently still depends on drone/ca-certs, which I think should be dropped.

[anbraten]

I already started on doing that in #257

To test the UI rewrite ATM the easiest way is currently to checkout that branch and run woodpecker via the debug with vs-code.

[UnlimitedCookies]

Awesome, that PR already looks promising.

I am still wondering though why there are still two very similar docker images (one ending with .alpine).

[anbraten]

Without alpine is the scratch image with just the binaries in it and with .alpine is an image based on alpine so you are able to use a command line. I prefer the scratch images, but some others like to have a command line next to woodpecker so we have both.

[UnlimitedCookies]

I understand, thanks for the explanation!

Even better would it be to just let docker handle the building with a docker-compose.yml. Is that currently possible?