Fix mypy issue with name and fullname being properties

[pbabics]

Mypy plugin issue changeog:
python/mypy#6617

Fix based on https://github.com/samuelcolvin/pydantic/pull/1058/files#

Mypy traceback:

(edge) ntx@ntx-pc ~/Projects/quantlane/market-making-tracker (master) $ mypy . --show-traceback
/home/ntx/.pyenv/versions/3.8.2/envs/edge/lib/python3.8/site-packages/mypy/typeshed/stdlib/3/enum.pyi:29: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.770
Traceback (most recent call last):
  File "mypy/semanal.py", line 4679, in accept
  File "mypy/nodes.py", line 1062, in accept
  File "mypy/semanal.py", line 1930, in visit_assignment_stmt
  File "mypy/semanal.py", line 2301, in process_type_annotation
  File "mypy/semanal.py", line 4771, in anal_type
  File "mypy/types.py", line 451, in accept
  File "mypy/typeanal.py", line 160, in visit_unbound_type
  File "mypy/typeanal.py", line 216, in visit_unbound_type_nonoptional
  File "mypy/typeanal.py", line 850, in anal_array
  File "mypy/typeanal.py", line 857, in anal_type
  File "mypy/types.py", line 451, in accept
  File "mypy/typeanal.py", line 160, in visit_unbound_type
  File "mypy/typeanal.py", line 196, in visit_unbound_type_nonoptional
  File "/home/ntx/.pyenv/versions/3.8.2/envs/edge/lib/python3.8/site-packages/fastenum/mypy_plugin.py", line 466, in transform_enum_type
    f'{meta_info.fullname()}._EnumMetaType',
TypeError: 'str' object is not callable