fix mypy errors

this fixes two distinct mypy errors

one where NamedTuple/dataclassees can't be
defined locally
https://github.com/python/mypy/issues/7281

which happens when you run mypy like
mypy -p my.core on warm cache

the second error is the core/types.py file shadowing the
stdlib types module

my/arbtt.py

@@ -90,7 +90,7 @@ def entries() -> Iterable[Entry]:
 
 def fill_influxdb() -> None:
     from .core.influxdb import magic_fill
-    from .core.types import Freezer
+    from .core.freezer import Freezer
     freezer = Freezer(Entry)
     fit = (freezer.freeze(e) for e in entries())
     # TODO crap, influxdb doesn't like None https://github.com/influxdata/influxdb/issues/7722