Test

refactor: migrate test-app package to TypeScript #2851

Job	Run time
Tests	2m 20s
Floating dependencies	1m 17s
ember-try: ember-lts-3.28	1m 8s
ember-try: ember-lts-4.4	1m 17s
ember-try: ember-release	1m 24s
ember-try: ember-beta	1m 2s
ember-try: ember-canary	1m 43s
ember-try: embroider-safe	1m 25s
ember-try: embroider-optimized	1m 27s
ember-try: ember-classic	1m 42s
	14m 45s

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