R1:afc3099ee785

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…