Add top-level schema caches to Schema::Visibility for better performance #2595

Job	Run time
javascript_test	30s
lint	21s
postgres_test (gemfiles/rails_master.gemfile, 3.3, 1)	1m 53s
mongodb_test (gemfiles/mongoid_6.gemfile)	1m 30s
postgres_test (gemfiles/rails_7.1_postgresql.gemfile, 3.3)	1m 34s
system_tests	1m 47s
mongodb_test (gemfiles/mongoid_7.gemfile)	1m 24s
test (Gemfile, 3.2)	1m 43s
test (Gemfile, 2.7)	1m 14s
test (gemfiles/rails_7.0.gemfile, 3.1)	1m 48s
test (gemfiles/rails_master.gemfile, 3.2)	2m 40s
test (gemfiles/rails_7.0.gemfile, 3.2)	1m 29s
test (gemfiles/rails_7.1.gemfile, 3.3)	2m 0s
test (gemfiles/rails_master.gemfile, 3.3, 1)	2m 14s
test (gemfiles/rails_master.gemfile, 3.3, 1, 1)	2m 31s
	24m 38s

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