API: Deprecate NestedType.of in favor of builder

[rdblue]

This is a follow up to #12211. While adding support for default values in UpdateSchema, many of the changes were to use the NestedField builder's copy constructor, from(NestedField), so that field defaults are not dropped. Dropping defaults is easy to do when using the of factory method that was previously used to copy fields.

This PR deprecates that factory method and removes deprecated uses of NestedField methods.

[nastra]

@rdblue I believe you meant to also push changes that include a builder() method. Also I think it would be good to update all of the usages in SchemaUpdate to the non-deprecated methods

[rdblue]

Also I think it would be good to update all of the usages in SchemaUpdate to the non-deprecated methods

That's done in #12211. This will be rebased and merged after that one goes in.

[nastra]

LGTM, thanks @rdblue