[PORT] [activityfactory] Improve missing type error

[tomlm]

Port this change from botbuilder-dotnet/master branch:
microsoft/botbuilder-dotnet#3575

close: #3383
Remove the type checking and return the actual object if no type was found or type definition does not map to a supported activity type

So, if the LG output is {"key": "value"}, and no LG type(lgType) in the properties, string Activity would be returned.

if LG output contains lgType property, but it does not map to any supported types (activity, xxxCard, cardaction, adaptivecard, attachment. etc.), a warning would be throw shows that the current type is not supported. And finally, the text activity would be the result.

Changed projects

• Microsoft.Bot.Builder
• Microsoft.Bot.Builder.Dialogs.Adaptive.Templates.Tests

[LG,R9]