Backport "Fix #9879: allow top-level opaque type definitions in REPL" to 3.3 LTS#46

tgodzik wants to merge 5 commits intolts-3.3scala/scala3-lts:lts-3.3from

backport-lts-3.3-21753scala/scala3-lts:backport-lts-3.3-21753Copy head branch name to clipboard