Update context

[AndrewMusgrave]

WHY are these changes introduced?

Updating some context conversions described in #1403.

• export the result of React.createContext rather than provider/consumer
• use {Component}/context.tsx rather than {Component}/Components/Context/Context.tsx
• create the context type in the context file rather than a shared types file
• describe the context object in the render method to be more in line with function style components

WHAT is this pull request doing?

As described above for all contexts excluding withRef, which will be removed in v4.

Notes

• Kept my combines separate for now in case it makes 🎩 / review easier