mypy reports issues in the `tests` directory

[bradlarsen]

If you modify mypy.ini so that the files = manticore line is changed to files = manticore, tests, then mypy reports a number of issues within the tests directory:

tests/other/utils/test_config.py:130: error: Name 'test_parse' already defined on line 113
tests/ethereum/test_detectors.py:92: error: Incompatible types in assignment (expression has type "Type[DetectUnusedRetVal]", base class "EthDetectorTest" defined the type as "None")
tests/ethereum/test_detectors.py:112: error: Incompatible types in assignment (expression has type "Type[DetectSuicidal]", base class "EthDetectorTest" defined the type as "None")
tests/ethereum/test_detectors.py:134: error: Incompatible types in assignment (expression has type "Type[DetectExternalCallAndLeak]", base class "EthDetectorTest" defined the type as "None")
tests/ethereum/test_detectors.py:242: error: Incompatible types in assignment (expression has type "Type[DetectEnvInstruction]", base class "EthDetectorTest" defined the type as "None")
tests/ethereum/test_detectors.py:265: error: Incompatible types in assignment (expression has type "Type[DetectDelegatecall]", base class "EthDetectorTest" defined the type as "None")
tests/ethereum/test_detectors.py:304: error: Incompatible types in assignment (expression has type "Type[DetectRaceCondition]", base class "EthDetectorTest" defined the type as "None")
tests/ethereum/test_detectors.py:403: error: Incompatible types in assignment (expression has type "Type[DetectManipulableBalance]", base class "EthDetectorTest" defined the type as "None")
tests/native/test_state.py:213: error: Name 'testContextSerialization' already defined on line 160
tests/native/test_memory.py:1431: error: Not all arguments converted during string formatting
tests/native/test_cpu_manual.py:11: error: Incompatible import of "Memory" (imported name has type "Type[tests.native.mockmem.Memory]", local name has type "Type[manticore.native.memory.Memory]")
tests/native/test_cpu_automatic.py:6: error: Cannot resolve name "solver" (possible cyclic definition)
Found 12 errors in 6 files (checked 171 source files)

[bradlarsen]

We should fix the typing issues and change mypy.ini so that the tests subdirectory is checked by default.