ROUND() now properly supports INTEGER and DECIMAL

[TarantoolBot]

Root document: https://www.tarantool.io/en/doc/latest/reference/reference_sql/

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INTEGER and DECIMAL values passed as the first argument now will not be
cast to DOUBLE and the result will be of the same type as the first
argument. Also, the default type for the ROUND() is now DECIMAL.
Requested by @ImeevMA in tarantool/tarantool@5273b8c.