3.3.1-RC6 Release procedure

[Kordyjan]

• Backport relevant fixes:
  • Refine infoDependsOnPrefix #18204
    • Backport "Refine infoDependsOnPrefix" #18410
  • Do not compute protoFormal if param.tpt is empty #18288
    • Backport "Do not compute protoFormal if param.tpt is empty" #18411
  • revert Normalize match type usage during implicit lookup #17457
    • Revert "Normalize match type usage during implicit lookup" on 3.3.1 #18440
• Publish artifacts to Maven via CI
  • On release-3.3.1 branch:
    • In Build.scala: Set baseVersion to 3.3.1-RC6
    • In Build.scala: Set previousDottyVersion to 3.3.1-RC5
    • in changelogs add file with a changelog
    • Tag the branch as 3.3.1-RC6
  • https://github.com/lampepfl/dotty/actions/runs/5938113818
• On main:
  • In Build.scala: Set referenceVersion to 3.3.1-RC6
  • Set reference version to 3.3.1-RC6 #18471
• Announce the release
  • Publish release on GitHub Releases
  • Comment on the announcement thread on https://contributors.scala-lang.org