The existing set comparison method uses the prior elements with the computed
portions nulled out to find candidates to match the configuration. This
has the shortcoming of always removing optional+computed attributes,
because we have not yet found the configuration to know if attribute was
set or not.
Rather than having to take the most pessimistic value before comparison
to precompute the nulled values, we can compare each candidate directly,
walking the values in tandem. Each prior value is compared against the
config and checked to see if it could have been derived from that
configuration value, which allows us to treat optional+computed as
optional if there is config and computed if there is not.
This removes the ambiguity from having optional+computed attributes
within sets, giving us consistent plans when all values are known.
Unknown values of course are still undecidable, as are edge cases were
providers refresh with altered values or retained changed prior values
plan that were deemed not functionally significant.
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