Ensure UserActivity activities inherit from set activity

[mdrichardson]

Description

userActivity in the Node SDK didn't match the one in the .NET SDK, with respect to using activity.from in the activity property supplied in test.dialog files.

Specific Changes

• Added an else if condition to match .NET SDK, that sets activity.from to match the activity.from if passed in from the test.dialog file.

Testing

Added a test for UserActivity that would catch this as well as other things, since the test didn't exist.

The first Microsoft.Test.UserActivity is to check that it sets the adapter defaults. The next activity is to check that from gets set by the activity.from property. The next is to make sure it gets set by the user property

[coveralls]

Pull Request Test Coverage Report for Build 486587133

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.005%) to 84.475%

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Files with Coverage Reduction	New Missed Lines	%
libraries/adaptive-expressions/src/triggerTrees/trigger.ts	2	61.63%
libraries/botbuilder-dialogs-adaptive-testing/src/testActions/userActivity.ts	2	85.71%

Totals
Change from base Build 481448147:	-0.005%
Covered Lines:	17812
Relevant Lines:	20142

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💛 - Coveralls