Move `client/web/src/auth/Steps` to `wildcard/components` folder

Problem statement

The stepper component is defined in the auth folder. But it's a general component that should live in the Wildcard component library.

Success criteria

1. The Steps folder should be moved to client/wildcard/src/components/Steps
2. Components and hooks defined in the Steps folder should be re-exported in client/wildcard/src/components/index.ts
3. Components consumers should use yarn workspace imports. e.g., import { useSteps } from '@sourcegraph/wildcard'