Cleanup error message components

[mlqn]

We currently use different components to show error messages when an error occurs while fetching data, which leads to some visual inconsistencies.
I suggest creating one generic component based on Alert component from designsystem.

Dashboard

UI Editor

Prosess

Error boundary

[nkylstad]

Create a StudioComponent -> "PageError" or something similar.
Use this component across when there is an error on a page.
Could find relevant places to use the new component by checking for isError from useQuery.

[Annikenkbrathen]

I suggest we use the alert from the design system when creating the component "Page-error".
We should be consistent with the placement as well.

(OBS the warning component has new design and should be updated)

I suggest placing the component center-aligned at the top, with some space between the header and the component, to make it stand out more and draw attention

[mlqn]

The ErrorBoundary alert can't be tested as it stopped working after upgrading react-router-dom (see #13248). I will update the alert when I fix the issue.

[mlqn]

I noticed that error messages of the overview do not exactly have the same visual as one uses an Alert from Designsystem while the other uses the new StudioPageError component.

I don't think the error in the News section should use the StudioPageSpinner component, as it does not need margins or a title.

We might consider doing as we did with the spinner (StudioPageSpinner, StudioSpinner) and dividing the StudioPageError component into two components:

• StudioPageError for page-level errors that need margins and possibly a title as well
• StudioError for simple errors like those in the screenshot above 🤷‍♂️

[mlqn]

I also noticed an error in a title of the UX editor errors:

[framitdavid]

I also noticed an error in a title of the UX editor errors:

I think my PR which is about Error Boundary would change this. Since within my PR I let the router handle the page errors. #13304

[JamalAlabdullah]

I created this new issue to create a new component StudioError and use it instead of alerts with severity.