Backported fixes

• Refutable extractor may be an Apply tree #15651
• Bump compiler-interface and capture the diagnosticCode #15565
• Support Mirror synthesis for local and inner classes #15847

Contributors

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

According to git shortlog -sn --no-merges $3.2.0-RC3..3.2.0-RC4 these are:

     2  Chris Kipp
     2  Paweł Marks
     1  Jamie Thompson
     1  odersky