WIP Update gha

[c2main]

The main point here is to allow faster builds and regression testing.

So instead of building container image with pgaf source code included we build more specialized images without source code.

We then pass USE_DOCKER=1 to make in order to trigger building stages in docker, like this:

cd docs
make USE_DOCKER=1 all

Also split the GHA workflow to select only jobs relevant given files changes.

For PR:

• no ci for docs changes
• no docs for !docs changes
• no latex for docs changes
• latex only for tikz changes
• linting always

For push: all run, no exception