R1:4fd4ec3d275d

Hide inlines one-by-one, instead of in a big group

Summary:
Ref T12616. Fixes T12153. Currently, when you hide inlines, they hide completely and turn into a little bubble on the previous line.

Instead, collapse them to a single line one-by-one. Narrowly, this fixes T12153.

In the future, I plan to make these changes so this feature makes more sense:

- Introduce global "hide everything" states (T8909) so you can completely hide stuff if you want, and this represents more of a halfway state between…