The CSS spec (CSS2 10.6.4 / CSS Position 5.3) says:
1. Compute tentative height without min/max-height
2. If result > max-height, re-solve with max-height as height
3. If result < min-height, re-solve with min-height as height
We already implemented this correctly for the width axis, but the
height axis tried to bake min/max constraints into the solve_for
lambda. This corrupted the constraint equation when solving for
height with auto height + min-height, since the height term couldn't
cancel itself out (it was inflated to min-height on subtraction but
stayed 0 on addition).
This caused abspos elements with top+bottom insets and min-height to
incorrectly get the min-height as their height, even when the
containing block was tall enough for a larger height.
