[contextual][test] Contextual type decomposition tests cleanup
[contextual][test] Contextual type decomposition tests cleanup

Summary:
Changelog: [internal]

1. Always use `Array<T>` instead of `T[]` to be consistent
2. Skip post inference check when setup types. Post inference checks do not affect the type, and we don't care about type errors in type setup code anyways.
3. Use context_optimizer instead of an ad-hoc type visitor to fully resolve a type.

Reviewed By: panagosg7

Differential Revision: D36484849

fbshipit-source-id: 52c1529d8a02201f4e5812e064dfca18d28b17ac

mroch/flow,mroch/flow,facebook/flow,facebook/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow,facebook/flow,mroch/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow