[Engineering] Lower time for botbuilder-dialogs tests

[denscollo]

Addresses #2338

Description

This PR optimizes the time for the botbuilder-dialogs tests having no impact in the code coverage numbers and reducing the execution time approximately from 4s to 3s.

Specific Changes

choices_channel.test.js

• Removed duplicated tests should return true for supportsSuggestedActions() with skype and 10 and should return false for supportsSuggestedActions() with skype and 11.
• Fixed eslint warnings.

choices_choiceFactory.test.js

• Created a variable called expectedActivity for Teams and Cortana tests.
• Fixed eslint warnings.

dialogSet.test.js

• Moved some ConversationState instances at the top of the describe to reuse the same instance.
• Fixed eslint warnings.

memory_dialogStateManager.test.js

• Moved some createConfiguredTestDc function calls at the top of the describe to reuse the same DialogContext instance.
• Removed duplicated test Should raise an error if getValue() called with an invalid scope..
• Fixed eslint warnings.

Testing