Updates fixturify-project from ^2.1.1 to ^7.1.3 (5 majors). The API changed substantially along the way, so the test helper and its consumers are updated to the new API. Net effect on the helper is a code reduction — the new upstream write() machinery replaces the helper's hand-rolled serialization.

Upstream breaking changes handled

• v3: the class is now a named export (const { Project } = require('fixturify-project')), and project.root was removed — project.baseDir is now the project directory itself (fixture files are no longer nested under an extra <name>/ folder inside the tmp dir).
• v5/v6: writeSync() and toJSON() were removed; writing is now the async write().
• v7: files passed to the constructor are deep-merged (no impact on these tests).

Changes

tests/helpers/fixturify-project.js

• writeSync() → async write(); buildProjectModel() / buildProjectModelForInRepoAddon() are now async and read the generated package.json back from disk.
• In-repo addons are no longer serialized into the parent's files (that relied on the removed toJSON()); the helper now tracks them and writes each one into lib/<name> using the regular write() machinery during the parent's write(). This deleted the old serialization code and, as a bonus, the file-moving workarounds in the per-bundle-addon-cache fixture helper.
• Dependencies created through addDependency/addDevDependency are constructed as EmberCLIFixturifyProject instances and handed to upstream via its public addDependency(project) overload (upstream's internal addDep hardcodes its own Project class since v5). This keeps nested usage like addon.addAddon(...) and engine.addReferenceDependency(...) working.
• 'Reference' (dev)dependencies — package.json entries whose files intentionally live elsewhere on disk — are injected via a small pkgJSONWithDeps() override. This overrides a private upstream method; there is currently no public hook for customizing the generated package.json.

Tests

• All writeSync() / buildProjectModel() call sites are now awaited.
• tests/helpers/per-bundle-addon-cache.js: the standard cache fixture now defines the shared test-addon-dep / test-engine-dep directly in PROJECT/lib (and removes them from the project's ember-addon.paths) instead of creating them nested and moving their serialized files around — same disk layout, much simpler.
• package-info-cache-test: the toJSON monkeypatch that left an empty node_modules/ember-resolver folder is replaced by explicitly emptying that directory after write(). Path assertions using fixturifyProject.root now use baseDir.
• proxy-test: expect(() => buildProjectModel()).to.throw(...) became await expect(...).to.be.rejectedWith(...) since the model builder is now async.

Behavioral change worth flagging

Upstream now writes devDependencies to node_modules after dependencies (v2's toJSON did the opposite), so when the same package name exists in both with different versions, the devDependency copy is what ends up on disk. The duplicated-addon expectations in instantiate-addons-test were updated from 1.0.0 to 2.0.0 accordingly (the addon ordering that test locks down is unchanged).

Also included

• A one-line prettier fix to RELEASE.md (separate commit) — prettier --check has been failing on master because of it, which keeps the linting CI job red.

Testing

• node tests/runner tests/unit/**/*-test.js: 979 passing, 0 failing
• pnpm lint (prettier + eslint): passing