Update GetValue to throw on error - HOLD

[ceciliaavila]

#minor

Description

This PR updates the GetValue method in ExpressionProperty to throw when there's an invalid expression.
This was reported as part of an issue in Composer where an invalid expression was causing an error in JS while .NET was letting it pass.
This PR also fixes an issue in the ConfirmInput class where an invalid expression was being ignored.

Specific Changes

• Updated the GetValue method in ExpressionProperty to throw in case of an error.
• Updated OnRecognizeInputAsync in ConfirmInput to use the GetChoiceOptionsAsync to retrieve the options from an lg template.

Testing

These images show the related unit tests passing after the changes.

[coveralls]

Pull Request Test Coverage Report for Build 344543

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 17 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.01%) to 79.092%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/AdaptiveExpressions/BuiltinFunctions/GetNextViableTime.cs	1	93.94%
/libraries/AdaptiveExpressions/BuiltinFunctions/GetPreviousViableTime.cs	1	93.94%
/libraries/Microsoft.Bot.Streaming/Payloads/StreamManager.cs	1	90.0%
/libraries/Microsoft.Bot.Builder.Dialogs.Adaptive/Input/ConfirmInput.cs	5	85.53%
/libraries/AdaptiveExpressions/ExpressionProperties/ExpressionProperty.cs	9	69.49%

Totals
Change from base Build 344537:	-0.01%
Covered Lines:	25815
Relevant Lines:	32639

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💛 - Coveralls