Make resolving fast

[jakemac53]

Now that the resolver is fixed, it appears to be dreadfully slow :(.

[jakemac53]

Looks like the current resolver from code_transformers (which we are using) isn't sharing sources between resolvers. This is probably because it had no info about phases since it was built on top of pub, but since we are building in support we should be able to be better. Unfortunately that means re-implementing all the functionality for this package :(.

[jakemac53]

One consideration here is tracking which files are used. Since in the optimized version it won't actually be reading all inputs each time (presumably) we will need to manually add all transitive imports as deps whenever you resolve a library.