Avoid redefining decompositions for non-parametric gates

[ajavadia]

What is the expected enhancement?

The unroller pass depends on decompositions that are defined per gate, and expands those gates according to those decomposition rules.

For gates such as crz, cu1, cu3, rx, ry, rz, rzz, u1, u2, u3, the decomposition depends on the parameter, and so each gate instance can have its own decomposition.

However, for all other gates, this is redundant and can start to add up. Instead, the decomposition should be defined once, for the class (not each instance).

[ajavadia]

closing as covered by #3800