Slider has two inputs

Currently the Slider component has two inputs with the same value, the actual slider thumb and the input field. This is causing problems with accessibility.

When the slider thumb moves, the value in the input box which is visible to sighted users isn't read out by the screen reader. The screen reader just keeps repeating "greater than".

Start by inspecting the Slider component, especially the slider thumb and the visible input field, then reproduce the behavior with a screen reader. Done means the current slider value is announced correctly when the thumb moves and the duplicate-input accessibility problem is resolved.

Written by the indexing model from the issue text.