feat: Store/Cache Support for RequestManager

[runspired]

Implements Store portion of RequestManager from emberjs/rfcs#860 as well as some associated bits of Cache v2.1 from emberjs/rfcs#854 to support it.

A probably incomplete list of the changes necessary:

• record-data => cache
• @ember-data/record-data => @ember-data/json-api
• Store._notificationManager => Store.notifications
• deprecate StoreWrapper.recordDataFor
• deprecate Store.createRecordDataFor
• deprecate Store.instantiateRecord extra args
• Add Store.request
• Add Store.requestManager
• ember-data auto-configures RequestManager
• add Cache.put
• add Cache.peekDocument
• add Cache.peek(<doc>)
• add legacy-handler
• add request-utils
• refactor existing request methods to utilize request-manager