Support for unique_rowid function

[mrmntte]

A row_uniqueid function like the one in CockroachDB that generates 64-bit ids.
"The function generates a default value from the timestamp and ID of the node executing the insert. Such time-ordered values are likely to be globally unique except in cases where a very large number of IDs (100,000+) are generated per node per second. Also, there can be gaps and the order is not completely guaranteed."

https://www.cockroachlabs.com/docs/stable/serial.html#example