Improve memory consumption of Parameter and Parameters

Hey,

I recently noticed in our loadtests a small but noticeable heap pressure coming from Parameters and Parameter. Some ArrayLists are initialized without an initial capacity although they are known in those cases - which in the end is not critical but also not optimal. Additionally, there is one call to gather the return type of a method, that constructs a ClassTypeInformation and the underlying map for the type variables which could be saved in some cases.

I attached a small PR to optimize those places.

Cheers,
Christoph