Update markup and signature exit model with new styling

[grzesiek2010]

Closes #6117

Why is this the best possible solution? Were any other approaches considered?

The new dialog is similar to the one we display on quitting a form so the implementation is also similar. Nothing special to discuss here.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

We need to test the three widgets:

• Signature widget
• Draw widget
• Annotate widget

to confirm the dialog displayed on quitting the drawing screen works well. I don't think there is anything else risky that should be tested.

Do we need any specific form for testing your changes? If so, please attach one.

No, we can use the All question types form from the demo server.

Does this change require updates to documentation? If so, please file an issue here and include the link below.

No.

Before submitting this PR, please make sure you have:

• added or modified tests for any new or changed behavior
• run ./gradlew connectedAndroidTest (or ./gradlew testLab) and confirmed all checks still pass
• added a comment above any new strings describing it for translators
• added any new strings with date formatting to DateFormatsTest
• verified that any code or assets from external sources are properly credited in comments and/or in the about file.
• verified that any new UI elements use theme colors. UI Components Style guidelines

[seadowg]

I can't see any test coverage for these 3 buttons - I'm guessing that's an existing problem though. This is probably a good opportunity to add it (maybe as part of a DrawActivityTest).