Incorrect onView activation event generation

[msujew]

Bug Description:

Since #12167 we automatically determine the activation events depending on certain other entries in the contributes part of the package.json. This doesn't work correctly as the views part isn't correctly generated.

Steps to Reproduce:

1. Download and install this extension.
2. Open the view and see that it's empty because the extension hasn't been activated yet.
3. Reload the app, run the Add Colors command and open the view again. It's now populated because the extension has been activated.

Additional Information

• Operating System: Any
• Theia Version: 1.43.1