🔨 Switch ChangeSubscription to use useOvermind

[MichaelDeBoey]

Follow-up of #2654

Things I did extra:

• Change updateSubscriptionClicked's signature to accept a string instead of { coupon: string }, because it only has 1 argument
• Put all styles into the elements.ts file
• Move overmind subscriptions as close as possible to the components itself instead of passing it through
• Type StripeInput's onChange prop
• Type LinkButton's onClick prop

[lbogdan]

Build for latest commit a6d5197 is at https://pr3055.build.csb.dev/s/new.

[SaraVieira]

Awesome!!