fix(arborist): respect --omit flag in linked install strategy

[manzoorwanijk]

In continuation of our exploration of using install-strategy=linked in the Gutenberg monorepo, which powers the WordPress Block Editor.

Summary

npm install --omit=dev with install-strategy=linked silently installs all dependencies including devDependencies. The --omit flag has no effect because the isolated reifier's makeIdealGraph unconditionally traverses all edges without consulting the omit option.

The ideal tree nodes already have dev/optional/peer flags set by calcDepFlags, so the fix is to call shouldOmit() when traversing edges in makeIdealGraph to skip nodes that match the omit set.

References

Fixes #9065

[manzoorwanijk]

@wraithgar any idea why CI didn't trigger here?

[wraithgar]

@manzoorwanijk nope. Computer gremlins.

[wraithgar]

Looks like actions is having trouble this morning, if I had to guess. Don't worry about it, we wouldn't release till next week so there is no rush here.

ETA: no need to guess https://www.githubstatus.com/incidents/g5gnt5l5hf56

[manzoorwanijk]

Seems to be fine now.