Replace react-numeric-input package

[didoesdigital]

This PR primarily replaces the react-numeric-input package because it uses outdated lifecycles that's no good for upgrading to React 18 and the package is unmaintained: Warning: componentWillReceiveProps has been renamed, and is not recommended for use. See https://reactjs.org/link/unsafe-component-lifecycles for details.

The approach taken in this PR is to remove the package and build the needed features directly into Typey Type.

There are some slight differences:

• replaces <b> with <button> elements
• adds ARIA labels like aria-label="Increment"
• the numeric input now clamps values on blur
• the numeric input no longer snaps to nearest step value
• the numeric input no longer displays 1 as 1.0 in the Diagram size field (it now shows 1, 1.1, etc)
• the numeric steppers no longer support click and hold to zip through numbers quickly
• the stepper button icons are slightly bigger

This PR also bundles in some other changes:

• extracting prompt-related functions for tests and renaming prompts.tests.ts
• fixing up some scss
• fixing some types