Fix #9879: allow top-level opaque type definitions in REPL (#21753) #32903

Job	Run time
test	59m 5s
test_non_bootstrapped	30m 7s
test_scala2_library_tasty	0s
MiMa	11m 49s
test_windows_fast	0s
test_windows_full	1h 1m 20s
community_build_a	56m 36s
community_build_b	1h 29m 28s
community_build_c	1h 10m 56s
test_sbt	18m 30s
build-msi-package	0s
test_java8	0s
build-sdk-package / build	7m 48s
build-chocolatey-package / build	20s
test-chocolatey-package	0s
publish_nightly	0s
publish_release	0s
nightly_documentation	0s
open_issue_on_failure	0s
	6h 45m 59s

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