Expansion fuel for pending wanted and pending given constraints
Fix for #21909 (closed)
CDictCan.cc_pend_sc now is a counter called ExpansionFuel
instead of a boolean flag. This counter acts as fuel to restrict unnecessary wanted superclass expansions. Wanted constraints with pending superclass expansion get a fuel of 1, while Given Constraints get a fuel of 3.
The Note [Expanding Recursive Superclasses and ExpansionFuel] talks about the motivation of the change in detail