fix: [#4568] scoreThreshold no longer works in 4.17.0 and later

[ceciliaavila]

Fixes #4568

Description

This PR reverts part of the changes in PR #4208 where the function that filtered the QnAMaker results using the score threshold value set in the QnAMaker options was removed.
It also includes a condition to skip the filter when the returned answer is the QnAMaker default answer.

Specific Changes

• Adding back the sortAnswersWithinThreshold function in generateAnswerUtils.ts.
• Restored the call to the sort function in the QnAMaker class before returning the results.

Testing

These images show the results returned when a score threshold is set with a value of 0.65:

[coveralls]

Pull Request Test Coverage Report for Build 7049330782

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• 9 of 9 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.009%) to 84.645%

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Totals
Change from base Build 7048575548:	0.009%
Covered Lines:	20346
Relevant Lines:	22770

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💛 - Coveralls