Allow clippy::needless_update in Builder::build

[benediktsatalia]

This removes a lot of clippy warnings for factori usages that have defaults for all fields of a struct which makes the ..factori::Default::default() a needless update. This is ignores the warnings for this from clippy.

[andrewswait]

@mjkillough any objections to merging this? In the meantime I've added #[non_exhaustive] to a bunch of my structs to get rid of the noise when running clippy.