Java: Add Callable.getErasureStringSignature()

[Marcono1234]

I assume the intention behind Callable.getStringSignature() is to provide a concise representation of the signature. However, there are two problems with the representation of parameter types:

• It depends on Type.toString() which has no guaranteed format
• For parameterized types, it includes all type arguments
  • This makes usage quite verbose, e.g. doSomething(Function<? super Integer,? extends String>)
  • The type arguments are separated only by a comma, but not by a space (unlike the callable parameter types)

This defeats the purpose of getStringSignature() a bit. This could be solved by adjusting the getStringSignature() implementation, but I chose to instead add a separate predicate called getErasureStringSignature().

Open questions:

• Should the existing getStringSignature(), hasStringSignature(string) and paramsString() be deprecated?
• With the new getErasureStringSignature(), might the erasure for type variables be too error-prone? E.g. you have to know how the erasure is determined and check the bounds for the variable. On the other hand, the question is to what extend the name of a type variable can be considered an implementation detail (which might change between versions).

Any feedback is appreciated!

[Marcono1234]

Have rewritten this to use concat. The public Git history did not indicate why this was previously implemented this way. So if there are any internal reasons for this, I can revert the change if you want.