feat: edge.explain - include bundled flag

[kumavis]

when analyzing a dep graph its useful to see if an Edge is a bundledDependencies edge. this is especially useful when trying to understand the provenance of a package's content.

This PR adds a bundled flag to the Edge.prototype.explain result to indicate if his dependency linkage is a bundled dependency.

Alternate Implementation

instead of just adding this to the Edge.prototype.explain result, it could be added (e.g. as a getter) on the Edge.prototype itself, allowing for the package consumer to inspect if an edge is a bundledDependencies edge or not.

References

Related to npm/cli#2750

[kumavis]

cant get tests to pass locally due to some anomalous error https://gist.github.com/kumavis/ab6db08a4ab7231e406beeab5815acea

[kumavis]

the anomalous error is preventing me from properly updating the snapshots

[kumavis]

also-- is this normal?

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	test/arborist/build-ideal-tree-peer-dep-override-with-dep-sets-being-replaced/
	test/arborist/build-ideal-tree/
	test/arborist/reify-reify-properly-with-all-deps-when-lockfile-is-ancient/
	test/arborist/reify/

[kumavis]

the tests pass when i run them individually e.g.: npx tap test/arborist/build-ideal-tree.js

[kumavis]

closing in favor of #241