Make `_setup_next_sequence` usable with `DictFactory` subclasses #613

Job	Run time
Python 3.8, Database sqlite	1m 10s
Python 3.8, Database postgres	1m 11s
Python 3.9, Database sqlite	1m 14s
Python 3.9, Database postgres	1m 17s
Python 3.10, Database sqlite	1m 35s
Python 3.10, Database postgres	1m 37s
Python 3.11, Database sqlite	1m 5s
Python 3.11, Database postgres	1m 6s
Python 3.12, Database sqlite	36s
Python 3.12, Database postgres	33s
Python pypy-3.9, Database sqlite	1m 57s
Python pypy-3.9, Database postgres	1m 58s
Python pypy-3.10, Database sqlite	1m 56s
Python pypy-3.10, Database postgres	2m 3s
	19m 18s

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