[FEATURE] Allow visualizing the dashboard's JSON in read mode

[AntoineThebaud]

Description

The button to access the dashboard's JSON in the toolbar is now accessible in read mode too, allowing the users to view the JSON definition of the dashboard without being able to edit it.

Screenshots

2023-12-15_15h52_23.mp4

Checklist

• Pull request has a descriptive title and context useful to a reviewer.
• Pull request title follows the [<catalog_entry>] <commit message> naming convention using one of the
  following catalog_entry values: FEATURE, ENHANCEMENT, BUGFIX, BREAKINGCHANGE, DOC,IGNORE.
• All commits have DCO signoffs.

UI Changes

• Changes that impact the UI include screenshots and/or screencasts of the relevant changes.
• Code follows the UI guidelines.
• Visual tests are stable and unlikely to be flaky.
  See Storybook
  and e2e docs for more details. Common issues
  include:
  • Is the data inconsistent? You need to mock API requests.
  • Does the time change? You need to use consistent time values or mock time utilities.
  • Does it have loading states? You need to wait for loading to complete.

[Gladorme]

LGTM 😄