[Accessibility] Slide Viewer: Form elements don't have labels

[nwanduka]

Describe the bug The following form elements on the slide viewer page do not have an accessible label:

1. Zoom buttons
2. Form fields in the Upload model modal (when you click the 'segment' tool in the toolbar)

To Reproduce Steps to reproduce the behavior:

1. Open a slide to view
2. Click on 'Segment' in the tool bar
3. Click on 'Add model'
4. Then run the Axecore devtools to see error.

Expected behavior Every form element must have an accessible label that screen readers can call out.

Screenshots