Add a view option to disable blame in Diffusion and fix some view transition bugs

Summary:
See PHI604. Ref T13130. Ref T13105. There's currently no way to turn blame off in Diffusion. Add a "Hide Blame" option to the "View Options" dropdown so it can be toggled off.

Also fix a couple of bugs around this: for example, if you loaded a Jupyter notebook and then switched to "Source" view, blame would incorrectly fail to activate because the original rendering of the "stage" used an asynchronous engine so willRenderRef() wasn't called to populate blame.

Test Plan:

• Viewed a source file, toggled blame off/on, reloaded page to see state stick in URL.
• Viewed a Jupyter notebook, toggled to "Source" view, saw blame.
• Viewed stuff in Files (no blame UI options).
• Tried to do some invalid stuff like toggle blame on a non-blame engine (options disable properly).

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13130, T13105

Differential Revision: https://secure.phabricator.com/D19414