[Drivers] Make component drivers work for function components with Hooks

[conor-cafferkey-sociomantic]

Currently

Nessie provides a suite of component drivers for use in tests with Enzyme full-DOM rendering.

Problem

Currently the implementation of the drivers assumes that all components are classes not functions. But in Milestone-Hooks! we’re converting all components to functions, so everything breaks 😬

Wanted

Update all component drivers to work with function components. This implies we need to find a way to access the theme context inside the drivers... or find an alternative way of targeting elements.