Backported chnages

• Add ErrorMessageID to -Winfer-union warnings (#25073) #25249
• Warn if for with many vals and overloaded map #25090
• Recognize Nullable annotations in explicit nulls #25237

Contributors

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

According to git shortlog -sn --no-merges 3.8.2-RC2..3.8.2-RC3 these are:

     3  noti0na1
     3  Wojciech Mazur
     1  Som Snytt