ReviewRequestPageEntry instances were previously told what their

collapse state was, as this was originally calculated in the view. As

this was restructured to allow for page entry type registration and

dynamic updates to the page, the collapsing logic was more closely tied

to each entry.
Entries no longer need to be told their collapsed state, so instead,

entries now calculate it themselves. They have a new

calculate_collapsed method that's called by a collapsed cache

property. These can make use of the new ReviewRequestPageData

association to figure out what the collapsed state should be.
Once set, the collapsed value is not changed for the instance. This

means that instead of other methods (like add_comment) altering the

pre-computed value, their logic is now incorporated into the initial

computation, making for more predictable and testable results.
Function signatures are now more simplified because of this, and

extension authors will be able to make better use of sane defaults for

the collapsing states.
Unit tests have been updated to check all the various collapsing states.
An upcoming change will build upon this to improve the logic we have for

calculating collapse states for reviews and anything with status

updates.

Unit tests pass.
Tested with a large review request containing every type of data used for

collapse states. Verified that the collapse states were consistent before

and after this change.