Remove the Unused codes and styles

[Aby-JS]

Why

We need to remove the unused old react-sdk package, react components, shared-ui styles and also refactor the new styles.

TODOS

• [x] Remove react-sdk package and move the useCorbado hook and related contexts to react package.
• [x] Delete unused components in react package.
• [x] remove the old styles from shared-ui package.
• [x] Refactor the new style sheet by breaking it into multiple style sheets and go through all the names of CSS classes and check if they follow the naming convention properly

Acceptance criteria

• [x] No dependency on react-sdk
• [x] Well organized stylings in shared-ui
• [x] All functionalities are working as they were before changes

[incorbador]

yes makes sense, we should first merge feature-refactor-to-thin-frontend to develop