MONGOID-5810 Don't leak internal state via `#as_document` #3771

Job	Run time
ruby-3.2 driver-current mongodb-6.0 replica_set	12m 45s
ruby-3.1 driver-current mongodb-6.0 replica_set	12m 49s
ruby-3.0 driver-current mongodb-6.0 replica_set	13m 10s
ruby-3.1 driver-master mongodb-6.0 replica_set	13m 7s
ruby-3.0 driver-stable mongodb-6.0 replica_set	12m 42s
ruby-3.3 driver-current mongodb-7.0 server	11m 41s
ruby-3.2 driver-current mongodb-7.0 server	10m 53s
ruby-3.2 driver-current mongodb-7.0 server	11m 1s
ruby-3.1 driver-current mongodb-7.0 server	10m 41s
ruby-3.1 driver-current mongodb-6.0 server	10m 41s
ruby-3.0 driver-current mongodb-6.0 server	11m 0s
ruby-3.0 driver-current mongodb-6.0 server	10m 59s
ruby-2.7 driver-current mongodb-6.0 server	10m 49s
jruby-9.3 driver-current mongodb-6.0 server	18m 46s
ruby-3.1 driver-current mongodb-5.0 replica_set	12m 22s
ruby-2.7 driver-current mongodb-4.4 replica_set	12m 55s
	3h 16m 21s

Provide feedback