Add seeded versions of deserialize functions.

[ghost]

Allows usage of DeserializeSeed types.

The T parameters on _seed functions are required because it's not possible to extract S::Value out of the higher-rank bound without also specifying that for all 'de, S::Value is indeed the same type.

[dtolnay]

Thanks!

Could you please move the new functions to a serde_yaml::seed module? These are going to be pretty niche so I would prefer that they don't appear as a distraction in the top level rustdoc view.

[ghost]

All done!

[dtolnay]

Looks good, thanks.

[dtolnay]

Published in serde_yaml 0.8.11.