[analyzer] Add forwarding `addVisitor` method

The majority of all `addVisitor` callers follow the same pattern:
  addVisitor(std::make_unique<SomeVisitor>(arg1, arg2, ...));

This patches introduces additional overload for `addVisitor` to simplify
that pattern:
  addVisitor<SomeVisitor>(arg1, arg2, ...);

Differential Revision: https://reviews.llvm.org/D103457