Add annotation to allow passthrough default methods on assisted factories

[jpenilla]

Fixes #1345

Add @PassthroughDefaultMethods annotation to allow using default methods on assisted factories (but only when explicitly requested by the user, see #1347 (comment))

As mentioned in the linked comment, we don't want to change existing behavior in case anyone is relying on it. So instead we add an annotation to specify what behavior we want. If the annotation was only able to be placed on individual methods, a more generic name like @Unassisted might be ok, however since I am also allowing the annotation on factory interfaces, I felt a more specific name made sense.

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