Update design for inputs.

Zeplin: https://zpl.io/p1YYqjM

Also: we have the organisms/joined-ui component, currently used only for buttons. Adapt inputs to use the same approach for their rounded corners.

Zeplin: zpl://components?stid=63079b90d0bf4a646c46c227&coids=63628af4d50639b5e763fbf8