ReflectionHelpers: Re-throw unchecked exceptions when invoking reflectively

Brought consistency to the handling of unchecked exceptions/errors across all of the reflective execution helpers (instance, static & constructor). All will now rethrow any unchecked exceptions and wrap checked exceptions in a `RuntimeException`. (Previously only instance methods did this and only for `RuntimeException`s, not `Error`s).

Also took the opportunity to get rid of the raw types in ReflectionHelpers.