tests: Move beam under toxgen #3151

Job	Run time
Gevent (pinned) (3.12, ubuntu-22.04)	7m 23s
Gevent (pinned) (3.8, ubuntu-22.04)	6m 15s
Gevent (pinned) (3.6, ubuntu-22.04)	3m 50s
Gevent (pinned) (3.10, ubuntu-22.04)	6m 34s
Gevent (pinned) (3.11, ubuntu-22.04)	6m 37s
All pinned Gevent tests passed	3s
	30m 42s

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