Don't unwrap automatically for Number to Datastore Types

[crwilcox]

Related to #754, #759

Remove auto inference of Numbers. This is a 'foot-gun' in the library and we should encourage usage of datastore.double and datastore.int so the library doesn't choose poorly.

This is for sure used in Save and Query today.

Note: breaking change.

[vicb]

It would be nice to create a migration path for DB created before inference is removed.

In such DB there could be a mix of integer/float for the same property and datastore.double / datastore.int would only apply to numbers created after the inference is removed.

[crwilcox]

Going to block on this happening for a bit. Warning may be enough and is in PR, tracked by 759.