MONGOID-5810 make sure we don't leak internal state via as_document (… #3862

Job	Run time
ruby-3.1 driver-current mongodb-5.0 server	11m 2s
ruby-3.1 driver-current mongodb-5.0 replica_set	12m 44s
ruby-3.0 driver-current mongodb-5.0 server	10m 39s
ruby-3.0 driver-current mongodb-5.0 replica_set	12m 44s
jruby-9.3 driver-current mongodb-5.0 replica_set	21m 21s
ruby-2.7 driver-current mongodb-4.4 server	10m 46s
ruby-2.7 driver-current mongodb-4.4 replica_set	12m 19s
ruby-2.6 driver-current mongodb-4.0 server	1s
ruby-2.6 driver-current mongodb-4.0 replica_set	1s
ruby-2.6 driver-current mongodb-3.6 server	1s
ruby-2.6 driver-current mongodb-3.6 replica_set	1s
ruby-3.1 driver-master mongodb-5.0 replica_set	12m 46s
ruby-3.0 driver-stable mongodb-5.0 replica_set	12m 14s
ruby-2.6 driver-oldstable mongodb-4.0 replica_set	1s
ruby-2.6 driver-min mongodb-4.0 replica_set	1s
ruby-2.6 driver-min mongodb-3.6 server	1s
ruby-3.1 driver-current mongodb-5.0 server	10m 53s
ruby-3.1 driver-current mongodb-5.0 server	10m 50s
ruby-3.0 driver-current mongodb-5.0 server	10m 40s
ruby-3.0 driver-current mongodb-5.0 server	10m 21s
ruby-3.0 driver-current mongodb-5.0 server	10m 58s
ruby-2.7 driver-current mongodb-4.0 server	1s
ruby-2.6 driver-current mongodb-4.4 server	10m 3s
ruby-2.6 driver-current mongodb-4.2 server	1s
ruby-2.6 driver-current mongodb-4.2 server	1s
ruby-2.7 driver-current mongodb-5.0 server	10m 47s
jruby-9.3 driver-current mongodb-5.0 server	19m 9s
	3h 30m 26s

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