Closes: #8137

Description

This PR updates the navigation after tapping the products onboarding banner CTA. Now we start the product creation flow immediately, without navigating to the Products tab first.

Changes

• Adds a PassthroughSubject to the dashboard view model (addProductTrigger), used to trigger the add product flow when the CTA is tapped.
• Adds the onProductCreated() callback to the product form view model, which is called when a new product is added so we can clear and resync the dashboard banner.
• Removes the code for MainTabBarController.presentAddProductFlow() that's no longer needed.

Testing

Because the banner is currently in an experiment, the easiest way to test it is to first comment out the experiment check:

Then proceed with testing:

1. Build and run the app.
2. Select a store with no products.
3. On the My Store screen, tap the "Add a Product" button on the onboarding banner. Confirm a bottom sheet appears to start the add product flow without changing screens.
4. Check the console and confirm the analytics event product_list_add_product_button_tapped was tracked.
5. Finish adding a product, and save it as a draft or publish it.
6. Go back and confirm you are returned to the My Store screen and the banner is gone.

Note: If you go back without saving or publishing the product, you can see you are returned to the My Store screen and the banner is still visible.

Screenshots

Tapping the banner CTA without product templates enabled:

Tapping the banner CTA with product templates enabled:

Submitter Checklist

Update release notes:

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.