WIP

I may break this into smaller parts since this is conceptually complicated (at least for me).

This depends on #1362 [Merged]

This pulls the preparation out of the compile phase. The sources contain the type information needed for compilation. All the sources type information is collected then the analysis is run and propagated across package boundaries. Once all the sources have been prepared, they can be compiled.

3. build system needs to be changed to collect generic instance information and propagate it across package boundaries. This would require reorganizing build package into loading all packages first, analyzing them, and then passing to the compiler, which is different from today's behavior where imported packages are loaded and compiled on-demand when compiler needs them. The tricky part here would be making sure build cache accounts for the fact that dependent packages may influence the set of generic instances of the dependency packages. - from this slack comment by nevkontakte