[PM-8220] New Device Verification (#5084)

* feat(BaseRequestValidator): 
Add global setting for new device verification.
Refactor BaseRequestValidator enabling better self-documenting code and better single responsibility principle for validators.
Updated DeviceValidator to handle new device verification, behind a feature flag.
Moved IDeviceValidator interface to separate file.
Updated CustomRequestValidator to act as the conduit by which *Validators communicate authentication context between themselves and the RequestValidators.
Adding new test for DeviceValidator class.
Updated tests for BaseRequestValidator as some functionality was moved to the DeviceValidator class.

test/Identity.Test/Wrappers/BaseRequestValidatorTestWrapper.cs

@@ -123,6 +123,11 @@ IBaseRequestValidatorTestWrapper
         Dictionary<string, object> customResponse)
     { }
 
+    protected override void SetValidationErrorResult(
+        BaseRequestValidationContextFake context,
+        CustomValidatorRequestContext requestContext)
+    { }
+
     protected override Task<bool> ValidateContextAsync(
         BaseRequestValidationContextFake context,
         CustomValidatorRequestContext validatorContext)