Resolution handler

[g-r-a-n-t]

This adds support for ingot dependencies on the file system. It includes significant changes to the resolver that make it more flexible. The new resolver is used in the driver crate to transitively initialize ingots and their dependencies via the init_ingot function. This driver function is used by both the language server and check subcommand to setup the input database. The resolver is also used directly in the tree subcommand to generate a tree representation of dependencies, without the overhead that would come from using the init_ingot function.

Followup items:

• Readd support for --core flag.
• Language server support for config dependency list updates.
• Spans in config diagnostics.
• Support for git urls.

[sbillig]

Readd support for --core flag.

I think we should drop support for specifying a custom core lib, and only support a custom std lib (when we figure out what the std lib should be). Core should be limited to things that wouldn't be interesting to replace. The compiler depends on core containing a certain set of traits and impls.

[micahscopes]

Overall looks good to me! Only changes I'd suggest are organizational:

• keeping the tree structure out of common crate since it's part of a pretty specific feature
• using less generic names for the dependency graph stuff in common

[micahscopes]

What's your thinking for keeping this in common vs in fe or in the resolver?

[g-r-a-n-t]

this is used in both the driver and fe crates to format trees. fe is off the table due to driver needing it and seeing as this module just deals with the printing of dependency trees I don't think it belongs in the resolver crate.

[micahscopes]

The naming in here seems pretty generic, any reason not to have more specific naming, even just at the module level? So that we could have something like dependencies::Graph or dependency_info::Graph? Or were you thinking this could potentially be useful for creating lots of different kinds of graphs, not just for dependencies?

[g-r-a-n-t]

I think this makes sense. the dependency tree formatting stuff could also be moved into that module, which would maybe make things a bit cleaner.

[micahscopes]

Loving all these consolidations 😎