frontend: range input widgets should support custom steps

[ES-Alexander]

Current behaviour

Dial Input widgets automatically have their values rounded to the nearest integer, while Slider Input widgets are rounded to the nearest 0.1, despite the elements themselves moving smoothly.

Expected or desired behaviour

1. Input widgets representing a range of numbers should have the step size as a configuration parameter
   • APIs don't always work in exact integer or 0.1 increments, so hardcoding them makes the widgets less useful than they could be, and may cause invalid data to be sent, or lose valuable fidelity in controls without a good reason to
     • As an example, a user may want to send quarter points between 0 and 1, which currently isn't possible - 0.25 and 0.75 can't be represented, and every representable value besides the mid and end-points would be invalid
2. The widgets themselves should then snap between those positions when being moved, to make it clear that the tooltip/label value is exactly the value being stored

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.