Redefine Tuple operations

This provides a way forward to fixing the signatures of some tuple
methods, and removes the inlining from the tuple methods. Optimization
will be implemented later directly on these method calls, which avoids
unnecessary complications due to inlining artifacts.

Fixes #12721
Fixes #16207

Author: nicolasstucki

compiler/test/dotc/pos-test-pickling.blacklist

@@ -63,6 +63,7 @@ i17149.scala
 tuple-fold.scala
 mt-redux-norm.perspective.scala
 i18211.scala
+i15743.scala
 
 # Opaque type
 i5720.scala