Applied clang-tidy modernize-use-equals-default fixes

This required some clean up, because the automatic changes borked a couple of files, but mostly resulted in stupid whitespacing. A few find/replace fixed things up.

There are now some duplicate semis because it did changes like:

  ~AMRIndexIterator() override{};
to
  ~AMRIndexIterator() override= default;;

Note there was a pointless semi before, which clang-tidy didn’t expect / account for.

My next commit will remove them.