[TASK] Parse `File` items into map

[kurtlawrence]

Goal

Definitions access is done immutably. This means that fetching Implementation or Type must already be added to the Defintions. Since adding types and impls may require other imports, the partition graph must already be established. Once it is established, the items can be parsed and added.

Aspects to Develop

• [ ] This may require some resolution smarts