In PHP we add collapsible classes to all elements except watchstar
so that certain tabs can be collapsed under the more menu in JS.
This adds unnecessary complexity to our codebase and is not used
if JS is disabled.
To simplify this and bring Vector's PHP consistency with core this
logic is moved to JavaScript.
Bug: T259372
Change-Id: I2acbf7089198118626368ee8a37615d2de062f83