MONGOID-5816: attr_readonly leaks into sibling classes (backport for 8.1) #3836

Job	Run time
ruby-3.2 driver-current mongodb-6.0 replica_set	13m 13s
ruby-3.1 driver-current mongodb-6.0 replica_set	13m 1s
ruby-3.0 driver-current mongodb-6.0 replica_set	13m 14s
ruby-3.1 driver-master mongodb-6.0 replica_set	13m 15s
ruby-3.0 driver-stable mongodb-6.0 replica_set	12m 29s
ruby-3.3 driver-current mongodb-7.0 server	10m 54s
ruby-3.2 driver-current mongodb-7.0 server	10m 50s
ruby-3.2 driver-current mongodb-7.0 server	10m 48s
ruby-3.1 driver-current mongodb-7.0 server	11m 2s
ruby-3.1 driver-current mongodb-6.0 server	11m 21s
ruby-3.0 driver-current mongodb-6.0 server	10m 46s
ruby-3.0 driver-current mongodb-6.0 server	10m 54s
ruby-2.7 driver-current mongodb-6.0 server	10m 42s
jruby-9.3 driver-current mongodb-6.0 server	19m 32s
ruby-3.1 driver-current mongodb-5.0 replica_set	13m 11s
ruby-2.7 driver-current mongodb-4.4 replica_set	13m 10s
	3h 18m 22s

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