Python tests can now be debugged by running them as embedded tests within NUnit

Fixed import hook replacing import error message

C# operator methods generate instance methods on the Python side like `__add__`. The arguments passed from Python are then processed by `MethodBinder`.

Co-authored-by: Victor <lost@losttech.software>

* Adds test cases for member changes during a domain reload

* Rework the serialization of reflected types

Serialization of System.Type, MemberInfo and MethodBase is now string
based. At deserialization, use reflection to attempt to recreate the
object, which may fail safely instead of throwing a
SerializaitonException during the deserialization of the whoie data
stream. Appropriate Exceptions will now be raised when the Maybe*'s
Value property.

ClassBase objects are now de-initialized and re-initialized in Reload
mode so that it's tp_dict picks up newly added members and removed
members no longer linger.

ModuleObject clears it's cache and remove cached members from it's
tp_dict.

Minor refactoring and modernization of MethodObject and MethodBinder

* Call PyType_Modified after modifying the type

Changing a type's attribute causes problem with it's cache. Force the
type to refresh itself when modifying it.

* Refactor the member binding logic of ClassManager

So that we can use that same logic when deserializing Maybe* types

* Include info about why deserialization failed in Maybe*

* Remove TestClassReference

The test case is covered in test_domain_relaod

Co-authored-by: Benedikt Reinartz <filmor@gmail.com>
Co-authored-by: Victor Milovanov <lost@losttech.software>

…ythonnet#1342)

Also added GetPythonThreadID

…net#1361)

Better error messages for method argument mismatch, Python to managed value conversion, and other problems.

- Converter.ToManaged obeys setError consistently
- PyObject_Hash and tp_hash return nint
- MakeGenericType and MakeGenericMethod have try/catch
- RaiseTypeError sets __cause__ instead of changing the message string
- PythonException.Normalize throws if an error is set
- AggregateExceptions print better from Python
- For an overloaded method, MethodBinder.Bind collects all binding errors with PythonExceptions as the inner.inner exceptions.
- ExceptionClassObject.tp_str calls Exception.ToString() instead of Exception.Message
(for justification see https://stackoverflow.com/questions/2176707/exception-message-vs-exception-tostring )
- Binding failures always have AggregateException as the cause, 
- Disabled test_method_parameters_change

…ers in Python, by returning the modified parameter values in a tuple.

BREAKING: MethodBinder omits a void return type when returning a tuple of out parameters.
DelegateManager unpacks a tuple of out parameters from Python (reversing the logic in MethodBinder) and sets the out parameters of the delegate.