Backported chnages

• Fix issues with Scala JS and the presentation compiler #25550
• Enforce JVM UTF-8 string limits in the backend #25300
• Fix class super-call invokespecial owner #25437
• Port the Scala2 optimizer #25165

Contributors

Thank you to all the contributors who made this release possible 🎉

According to git shortlog -sn --no-merges 3.8.3-RC2..3.8.3-RC3 these are:

    49  Solal Pirelli
     3  Wojciech Mazur
     1  Rikito Taniguchi
     1  Tomasz Godzik