[TS] Renderer and designer fixes

[dclaux]

Related Issue

Fixes #4767
Fixes #4734
References #4483

Description

• When toJSON() is automatically invoked via JSON.stringify(), it gets a parameter of type string. The AC renderer's implementation of toJSON() takes an optional parameter of type BaseSerializationContext. When the value of this parameter is not undefined, the code assumes it is of type BaseSerializationContext which is not the case when toJSON() is invoked via JSON.stringify(), and thus generates an exception. This PR fixes that by checking the type of the parameter toJSON() receives.
• The data structure generated from JSON would cause an exception when the JSON contained an empty array. The code now properly handles that case.
• New TextBlock elements created in the designer via drag/drop now have their wrap property set to true by default

How Verified

Verified manually in adaptivecards-designer-app and test site

Microsoft Reviewers: Open in CodeFlow

[ghost]

Hi @dclaux. Thanks for helping make the AdaptiveCards JS renderer + tooling better. As additional verification, once the JS build succeeds, please go to the test site to test out your website/designer changes.

[shalinijoshi19]

Hey @dclaux mind verifying the 3 changes also in the test site and including that little bit in the "How verified" section pls? https://adaptivecardsci.z5.web.core.windows.net/pr/4791