Block decomposition: another fix related to temporary terms refactoring

Temporary terms need to be computed per equation (as was done previously), and
not simply per block.

It’s necessary to track temporary terms per equation, because some equations
are evaluated instead of solved, and an equation E1 may depend on the value of
an endogenous Y computed by a previously evaluated equation E2; in this case,
if some temporary term TT of equation E2 contains Y, then TT needs to be
computed after E1, but before E2.