MONGOID-5610 - Cleanup: Use delegator for exists? on embedded proxy, and add code comments #3200

Job	Run time
ruby-3.2 drv:current db:6.0 rails: fle: replica_set	19m 46s
ruby-3.1 drv:current db:6.0 rails: fle: replica_set	13m 4s
ruby-3.0 drv:current db:6.0 rails: fle: replica_set	16m 3s
ruby-3.1 drv:master db:6.0 rails: fle: replica_set	20m 0s
ruby-3.0 drv:stable db:6.0 rails: fle: replica_set	20m 3s
ruby-3.1 drv:current db:6.0 rails:7.0 fle:helper server	15m 15s
ruby-3.1 drv:current db:6.0 rails:6.1 fle:helper server	18m 48s
ruby-3.0 drv:current db:6.0 rails:7.0 fle:helper server	14m 4s
ruby-3.0 drv:current db:6.0 rails:6.1 fle:helper server	12m 11s
ruby-3.0 drv:current db:6.0 rails:6.0 fle:helper server	15m 39s
ruby-2.7 drv:current db:6.0 rails:5.2 fle:helper server	8m 8s
jruby-9.3 drv:current db:6.0 rails:6.0 fle:helper server	29m 36s
ruby-3.1 drv:current db:5.0 rails: fle: replica_set	13m 14s
ruby-2.7 drv:current db:4.4 rails: fle: replica_set	12m 55s
ruby-2.7 drv:current db:4.0 rails: fle: replica_set	14m 19s
ruby-2.7 drv:current db:3.6 rails: fle: replica_set	14m 8s
	4h 17m 13s

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