Merged mypy.ini into setup.cfg (#27427)

Author: WillAyd

mypy.ini

@@ -166,3 +166,10 @@ skip=
     asv_bench/benchmarks/dtypes.py
     asv_bench/benchmarks/strings.py
     asv_bench/benchmarks/period.py
+
+[mypy]
+ignore_missing_imports=True
+no_implicit_optional=True
+
+[mypy-pandas.conftest,pandas.tests.*]
+ignore_errors=True