When cancelling an unsaved editing inline after a reload, don't cancel into an empty state

Summary:
Ref T13513. Overloading "original text" to get "edit-on-load" comments into the right state has some undesirable side effects.

Instead, provide the text when the editor opens. This fixes a cancel interaction.

Test Plan:

• Create an inline, type text, don't save.
• Reload page.
• Cancel.
• Before: cancelled into empty state.
• After: cancelled into deleted+undo state.

Maniphest Tasks: T13513

Differential Revision: https://secure.phabricator.com/D21219