[Enhancement] replace alerts to toasts in viewer

[mgautam98]

Description

Toast for no heatmap data instead of alert
Toast for no markup on annotation instead of alert
Documented functions inside viewer uicallbacks.js

• segment.js and model.js
  Changed name while deleting model to avoid confusion which was created in [Enhancement] Popup display in model and segment app #382 and [Enhancement] Model upload and delete UI #375

Motivation and Context

**Why is this change required? What problem does it solve?

• Documenting code is good for fast development.
• Replacing alerts with toasts to improve UX

Types of changes

**What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

**Go over all the following points, and put an x in all the boxes that apply.
**(If you're unsure about any of these, don't hesitate to ask. We're here to help!)

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[birm]

Thanks for:

• the ui improvement
• increasing our documentation coverage
• working with my comment