MONGOID-5810 Don't leak internal state via `#as_document` #3781

Job	Run time
ruby-3.2 driver-current mongodb-6.0 replica_set	12m 33s
ruby-3.1 driver-current mongodb-6.0 replica_set	12m 50s
ruby-3.0 driver-current mongodb-6.0 replica_set	12m 59s
ruby-3.1 driver-master mongodb-6.0 replica_set	13m 24s
ruby-3.0 driver-stable mongodb-6.0 replica_set	13m 2s
ruby-3.3 driver-current mongodb-7.0 server	11m 4s
ruby-3.2 driver-current mongodb-7.0 server	10m 35s
ruby-3.2 driver-current mongodb-7.0 server	10m 49s
ruby-3.1 driver-current mongodb-7.0 server	10m 55s
ruby-3.1 driver-current mongodb-6.0 server	10m 46s
ruby-3.0 driver-current mongodb-6.0 server	11m 14s
ruby-3.0 driver-current mongodb-6.0 server	11m 15s
ruby-2.7 driver-current mongodb-6.0 server	11m 4s
jruby-9.3 driver-current mongodb-6.0 server	18m 44s
ruby-3.1 driver-current mongodb-5.0 replica_set	12m 56s
ruby-2.7 driver-current mongodb-4.4 replica_set	12m 49s
	3h 16m 59s

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