This commit is a complete reimplementation of `wac-parser`'s resolution to be
based on `wac-graph`.

It also contains an overhaul of the `wac-graph` API to facilitate its use from
`wac-parser`:

* Reimplements `CompositionGraph` on top of `petgraph::StableDiGraph`, which
  eliminates needing to keep track of nodes internally to `CompositionGraph`.
* Packages now populate their type information into the graph's types
  collection rather than having their own collections.
* Splits the `Error` enum into discrete error types for each graph operation;
  this allows the AST resolver to properly attach span information to errors.
* Add type dependency edges for defined types, ensuring topological ordering.
* Fix encoding of defined type aliases so that each encoded alias refers to the
  export index of the previously encoded type.
* Added a debug formatter for `CompositionGraph` that outputs a DOT
  representation (used in resolution tests as well).
* Graph encoding now includes an optional producers custom section.
* Fixed toposort to be in ascending node index order for independent nodes.

The subtype checker implementation was reverted to the previous implementation,
where `invert` and `revert` are called at specific points to change the type of
check being performed; the newer implementation did not give the correct
"expected, found" error messages for AST resolution.

`wac resolve` now outputs a DOT representation of the resolved composition
graph instead of JSON.

Most of the deleted code comes from code that has already moved into
`wac-types` and `wac-graph`.

Closes #79.
Fixes #78.
Fixes #76.

Implements #37.

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

Co-authored-by: Ryan Levick <[email protected]>

This commit fixes an existing bug exposed by the refactoring (likely due to the
changes in the order in which nodes are processed for implicit arguments).

Previously, an interface might contain a type alias for another resource it
owns; this lead to the alias information of the resource being self-referential
for the interface containing the aliased resource.

It would then lead to infinite recursion in an attempt to remap such an
interface when populating implicit instantiation arguments.

The fix is to clear the self-referencing information while converting an
interface during package parsing.

Co-authored-by: Ryan Levick <[email protected]>