Another circular import in `mypy/test/testreports.py`

Bug Report

Running the testreports module in isolation reveals a circular import similar to #15570.

To Reproduce

$ tox r -e py311 -- mypy/test/testreports.py

Expected Behavior

It should collect the tests from the module.

Actual Behavior

______________________________________________________________________________ ERROR collecting mypy/test/testreports.py _______________________________________________________________________________
ImportError while importing test module '~/src/github/python/mypy/mypy/test/testreports.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/lib/python3.11/importlib/__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
mypy/test/testreports.py:7: in <module>
    from mypy.report import CoberturaPackage, get_line_rate
mypy/report.py:19: in <module>
    from mypy import stats
mypy/stats.py:11: in <module>
    from mypy.argmap import map_formals_to_actuals
mypy/argmap.py:8: in <module>
    from mypy.maptype import map_instance_to_supertype
mypy/maptype.py:3: in <module>
    from mypy.expandtype import expand_type_by_instance
mypy/expandtype.py:7: in <module>
    from mypy.types import (
mypy/types.py:3751: in <module>
    from mypy.expandtype import ExpandTypeVisitor
E   ImportError: cannot import name 'ExpandTypeVisitor' from partially initialized module 'mypy.expandtype' (most likely due to a circular import) (~/src/github/python/mypy/mypy/expandtype.py)

Your Environment

• Mypy version used: master
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: Python 3.11

Start with the tox command from the report and inspect the import chain from mypy/test/testreports.py through mypy/report.py, mypy/stats.py, mypy/argmap.py, mypy/maptype.py, mypy/expandtype.py, and mypy/types.py. Confirm the circular-import failure, then verify that running the test module collects its tests successfully.