[opt-viewer] Use Python 3-compatible iteritems

[modocache]

Summary

Replace a usage of a Python 2-specific dict.iteritems() with the
Python 3-compatible definition provided at the top of the same file.

Test Plan:
Run opt-viewer.py using Python 3 and confirm it no longer encounters a
runtime error when calling dict.iteritems().

[anemet]

LGTM, sorry :(.

[modocache]

Hey, no worries! I almost never catch Python 2/3 incompatibilities ahead of time. As I mentioned on PR34129, it'd be great to get some automated testing in place that could catch Python 2/3 errors as well, but until then I'm happy to fix these as I notice them.

Thanks for the review! :)

tools/opt-viewer/optrecord.py

class Remark(yaml.YAMLObject):
     # used as part of the key (in Python only immutable types are hashable).
     def _reduce_memory(self):
         self.Pass = intern(self.Pass)
         self.Name = intern(self.Name)
         self.Function = intern(self.Function)
 
         def _reduce_memory_dict(old_dict):
             new_dict = dict()
-            for (k, v) in old_dict.iteritems():
+            for (k, v) in iteritems(old_dict):
                 if type(k) is str:
                     k = intern(k)
 
                 if type(v) is str:
                     v = intern(v)
                 elif type(v) is dict:
                     # This handles [{'Caller': ..., 'DebugLoc': { 'File': ... }}]
                     v = _reduce_memory_dict(v)