[FormControl] Use stable context API

[eps1lon]

• move from deprecated context API to stable context API
• add withFormControlContext HOC to be able to access context via props without major component rewrite
• tried to move to DOM only testing whenever the test broke due to changed component tree
• minor propTypes fix (disableUnderline was spread to native div in InputBase)

Only the styling solution remains with the deprecated context API.

Closes #13465.

[oliviertassinari]

@eps1lon Awesome job! While I hate the fact it's increasing the n° of underlying components we use for a single input, I'm confident that we will be able to drastically improve that in v4 with the usage of the React hooks 💯.