3.3.1-RC7 Release procedure

[Kordyjan]

• Backport relevant fixes:
  • Tweak selection from self types #18467
    • Backport " Tweak selection from self types" #18475
  • revert Add reflect defn.FunctionClass overloads #16849
    • Revert "Add reflect defn.FunctionClass overloads" #18473
• Publish artifacts to Maven via CI
  • On release-3.3.1 branch:
    • In Build.scala: Set baseVersion to 3.3.1-RC7
    • In Build.scala: Set previousDottyVersion to 3.3.1-RC6
    • in changelogs add file with a changelog
    • Tag the branch as 3.3.1-RC7
  • https://github.com/lampepfl/dotty/actions/runs/6014684444
• On main:
  • In Build.scala: Set referenceVersion to 3.3.1-RC7
  • Set reference version to 3.3.1-RC7 #18483
• Announce the release
  • Publish release on GitHub Releases
  • Comment on the announcement thread on https://contributors.scala-lang.org