feat: add suggestionsActivityFactory & tests, fix QnAMakerDialog bugs

[stevengum]

Fixes part of #3464

Description

Adds type QnASuggestionsActivityFactory for developers to create a custom QnA Maker Active Learning Suggestions Activity to send to users. This provides a more extensive solution to customizing the Activity sent from the QnACardBuilder.getSuggestionsCard which relies on sending Hero Cards.

Through the use of a new constructor overload, developers can pass in this factory instead of the normal activeLearningCardTitle parameter. When developers use the factory, they must pass in the next parameter, cardNoMatchText. This parameter is used in both overloads by the dialog to allow users to indicate that the suggestions from QnA Maker didn't match what the user is asking.

There's a bug fix on onPreBubbleEvent() which should be ported to the other languages. If the incoming activity was a message but an error was thrown during the dialog's execution, it would try to call QnA Maker again. Which is an issue if the error was thrown while trying to call QnA Maker. I encountered this while using nock to ensure an Activity-like value was returned from
QnAMakerdialog.suggestionsActivityFactory and QnACardBuilder.getSuggestionsCard. The latter of which is a public static method, so it can be modified by Typescript developers during bot development.

Testing

Added unit tests

FYI @HesselWellema

[coveralls]

Pull Request Test Coverage Report for Build 699576726

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 16 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.02%) to 84.927%

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Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-ai/src/qnaMakerDialog.ts	16	86.53%

Totals
Change from base Build 699567022:	0.02%
Covered Lines:	18886
Relevant Lines:	21175

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💛 - Coveralls