[migration] Improve update of in-memory schema during 3.18 CWAttribute.defaultval change We weren't updating the schema properly so a bunch of structures still had the old rdef with 'String' as object. That caused failures to add new attributes later in the migration as their default value would be a Binary object but the schema would expect a String. Closes #3683640

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sql('DROP FUNCTION IF EXISTS _fsopen(bytea)')

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sql('DROP FUNCTION IF EXISTS fspath(bigint, text, text)')