Depending on timing when the query finishes, there can be
multiple internal EOF rows.

Move Crypto.SCRAM to __builtin.Nettle.Hash()->SCRAM analogous to
other similar APIs.

Crypto.SCRAM(Crypto.SHA256) is now Crypto.SHA256.SCRAM().

Also updates the testsuite and Sql.pgsql_util accordingly.

This reverts commit f342376c.

The race has instead been fixed correctly by:
pgsql: Cater for race during asynchronous destruction of bufcon.