Add missing Ix instances for tuples up to size 15

Summary

Both Haskell reports state that "A Haskell implementation must provide Ix instances for tuples up to at least size 15", but base only provides them up to size 5.

Haskell 98: https://www.haskell.org/onlinereport/ix.html#sect15.1
Haskell 2010: https://www.haskell.org/onlinereport/haskell2010/haskellch19.html#x27-22700019.2