Introduce ignore_column remove_never: true

What does this MR do and why?

This MR expands our ignore_columns helper for use cases where we don't want to remove it in the future. This helper was originally introduced for dropping columns. In such cases it was always temporary and would be removed after the column was actually dropped. But we also have started using it in some parts of the application where we have a column that is read-only so we need to hide it from Rails so that it doesn't do strange things like trying to set the value from a default loaded on the model.

Previously we hacked around this by using version 3000 or by calling ignored_columns += directly which is forbidden by a cop.

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