ShadeListBuilder clarity refactors

There are no functionality changes in this CL, just code structure:
* Standardize comparator code style
* Move list attach annulment into ListAttachState.detach()
* Add a TODO about the missing annulment

Bug: 237216329
Test: atest ShadeListBuilderTest
Change-Id: Id2d77e6bf9b89c4bae2026f2e5355542f1c76a20