Solve import cycles for mypy/expandtype.py and mypy/test/testtypes.py

[sobolevn]

Now it passes:

» pytest mypy/test/testtypes.py   
=================================== test session starts ===================================
platform darwin -- Python 3.11.3, pytest-7.3.2, pluggy-1.2.0
rootdir: /Users/sobolev/Desktop/mypy
configfile: pyproject.toml
plugins: cov-4.1.0, xdist-3.3.1
12 workers [116 items]    
.......................................s...................s....................... [ 71%]
.................................                                                   [100%]
============================= 114 passed, 2 skipped in 0.63s ==============================

I've also fixed this problem:

» python mypy/expandtype.py
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/mypy/mypy/expandtype.py", line 7, in <module>
    import mypy.type_visitor  # ruff: isort: skip
    ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/mypy/mypy/type_visitor.py", line 22, in <module>
    from mypy.types import (
  File "/Users/sobolev/Desktop/mypy/mypy/types.py", line 2968, in <module>
    from mypy.type_visitor import (  # noqa: F811
ImportError: cannot import name 'ALL_STRATEGY' from partially initialized module 'mypy.type_visitor' (most likely due to a circular import) (/Users/sobolev/Desktop/mypy/mypy/type_visitor.py)

Closes #15570

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅