Take account of angles when optimizing for TK2 gate count

[cqc-alec]

The standard FullPeepholeOptimize pass seeks to minimize the number of 2-qubit gates in the resulting circuit. When the target gate is TK2, this may be too crude a metric. For example, on Quantinuum devices the number of non-zero angles in the gate is important, and a cost function such as (0.3 + 0.7n) where 1<=n<=3 is the number of non-zero angles in the gate may be more appropriate.