Is there a nice reference for the finite dimensional (characteristic 0) representation theory of $GL_2(\mathbb Z/n\mathbb Z)$ and $PGL_2(\mathbb Z/nZ)$ for varying $n$ and in the limit, for $PGL_2(\mathbb Z_\ell)$?

I would like to know things like the number of irreducible representations, their dimensions, the minimal fields they are defined over and stuff like that.