Lateness for nested fields

Currently, lateness can only be defined for top level columns. In some use cases, users have a timestamp column in a nested field, for example a struct in a delta table. This feature would allow users to define lateness for a nested field.

We have lateness in tables and views. These are slightly different.

For a view this can be done by creating another local view which extracts the field to a column and applying lateness to that.
For a table this trick won't work.