Make component displayName the same as named exports

For example, the `ChromePicker` component's displayName is `Chrome`. Guess it would be better to keep the same name across. This should be helpful while writing tests of components that include one of these pickers. I was trying to assert if my component was rendering `ChromePicker` and spent a good few minutes before figuring out that the actual display name of the component is `Chrome`.

Happy to make a PR if this makes sense.

Start by locating the ChromePicker component and its displayName, then inspect the other picker exports for the same naming pattern. Confirm completion by checking that each component's displayName matches its named export and that component-rendering tests can refer to the exported names consistently.

Written by the indexing model from the issue text.