Evaluate MoreObjects.ToStringHelper add/addValue Overloading Performance

[romeara]

In Guava's ToStringHelper, the add and addValue methods were overloaded for primitives, in what appeared to be an attempt to to avoid auto-boxing for performance reasons.

In Alloy as of 0.1.0, we instead chose to only have the Object versions of the methods (initially) to avoid API bloat - we should evaluate how much of a performance difference the overloading provides, to determine if its worth adding into Alloy's version of the utilities