3.4.0-RC3 Release procedure

[Kordyjan]

• Merge Sync language.scala with main and backport "Add tests for context bounds migration" #19515
• Backport Handle default implicits to context parameters under -3.4-migration #19512
  • Backport "Handle default implicits to context parameters under -3.4-migration" #19518
• Publish 3.4.0-RC3 artifacts to Maven via CI
  • On release-3.4.0 branch:
    • In changelogs add file with a changelog
    • In Build.scala: Set baseVersion to 3.4.0-RC3
    • In Build.scala: Set previousDottyVersion to 3.4.0-RC3
    • Tag the branch as 3.4.0-RC3
    • Build
• Wait for confirmation from tooling:
  • Metals (@tgodzik)
  • Scala CLI
  • Scala Native (@WojciechMazur)
  • Scastie (@rochala)
  • Scala DAP
• On main:
  • In Build.scala: Set referenceVersion to 3.4.0-RC3
  • Check and update project/MiMaFilters.scala
• Announce the releases
  • Make GitHub releases public
  • Update the 3.4.0 tracking thread

[Kordyjan]

The artifacts are on maven central.

[tgodzik]

Metals works ok with 3.4.0-RC3