sql: COPY can't run outside of a transaction

[knz]

Using the attached input file import.sql.txt with psql one runs into the following error:

ERROR: txn: memory budget exceeded: 8 bytes requested, 0 bytes in budget

This is because the COPY statement binds its account to the transaction's memory monitor, and that is not yet initialized for an implicit transaction by the time the COPY statement is run (it runs somewhat earlier than the rest in execRequest).

Reported by @sploiselle