Make inline "ContentState" a client object, and track "hasSuggestion" on it

Summary:
Ref T13559. In an effort to ultimately fix the "quote + cancel" bug, begin formalizing content states on the client.

This creates a "ContentState" client object and moves the authoritative storage for the "hasSuggestion" property to it.

Test Plan: Created inlines, etc. See followups.

Maniphest Tasks: T13559

Differential Revision: https://secure.phabricator.com/D21645