MySQL-Connector-Net casts SEQ_IN_INDEX to uint and will
raise an exception if the type is a System.Int64.

As we don't support a huge number of multi-columns in
an index reducing to a uint is sufficient to represent
all values and maintain compatibility with MySQL-Connector-Net.

This matches the type (uint) returned by MySQL-8.3 and 8.0.

Reviewer: Alexander Barkov <bar@mariadb.com>