Centralize routes to avoid duplicating them

[mlqn]

Description

We might consider extracting / centralizing routes as constants (e.g. shared/src/constants.js or shared/src/routes.js or shared/src/dashboard-routes.js, ...) as we did for DASHBOARD_ROOT_ROUTE to avoid duplicating them.

Here are examples of duplicated strings for the /contact route :

https://github.com/Altinn/altinn-studio/blob/cd168f205b868c3d63c32711e84e2337af5a71fd/frontend/studio-root/app/App.tsx#L17

https://github.com/Altinn/altinn-studio/blob/cd168f205b868c3d63c32711e84e2337af5a71fd/frontend/packages/shared/src/components/ErrorBoundaryFallback.tsx#L23

https://github.com/Altinn/altinn-studio/blob/cd168f205b868c3d63c32711e84e2337af5a71fd/frontend/app-development/features/overview/components/Overview.tsx#L40

https://github.com/Altinn/altinn-studio/blob/cd168f205b868c3d63c32711e84e2337af5a71fd/frontend/app-development/features/overview/components/RepoOwnedByPersonInfo.tsx#L17

https://github.com/Altinn/altinn-studio/blob/cd168f205b868c3d63c32711e84e2337af5a71fd/frontend/app-development/features/appPublish/components/Deploy.tsx#L78

https://github.com/Altinn/altinn-studio/blob/cd168f205b868c3d63c32711e84e2337af5a71fd/frontend/packages/shared/src/contexts/ServicesContext.tsx#L75

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