Allow schema evolution in nested fields unrelated to generated columns

[Kimahriman]

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Description

Resolves https://github.com/delta-io/delta/issues/1281

Updating the schema of a field involved in generated columns is not allowed, because it could change the semantics of the generated field. However, the fields used by generated fields is only tracked at the top level of the schema. This updates the checks to track the full nested path to the field used by generated columns, so that other fields in those nested structs can be updated, as they are unrelated to the generated column.

How was this patch tested?

New and updated UTs.

Does this PR introduce any user-facing changes?

Adds new capability to update nested field types.