Adds a session attribute to count missed utterances

[richhaase]

Issue #, if available:

Description of changes:

This PR adds a session attribute that counts the number of consecutive missed utterances. This information allows us to exhibit different behavior depending on how many times a user asks a question that the QnA Bot is unable to answer.

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[abhirpat]

Thank you for your submission @richhaase. Could you please elaborate where and how you are using this information ? Have you had a chance to explore OpenSearch Dashboards for chat usage information like No Hits response satisfy your requirements?

[abhirpat]

Hi @richhaase, following-up on my previous message. Currently, no_hits are displayed in OpenSearch Dashboards > QnABot
Dashboard > No hits. If you're still needing this, please elaborate the use-case.

[israelias]

You can also just consider adding a lambda to the no_hits module that does the same thing plus more, in case you're trying to timeout and/or super-error-handle false on qnabot_gotanswer. But also consider how/why/when you would clear the count in case Kendra fallback is plugged to play as a feature on tie breaker, where every answer is not a hit -- to name one potential side effect to drill through. In any case I think your numerics have to be set as string values for sessionAttributes