Add visualization selector to analytics dashboard editor

What does this MR do and why?

Issue - #385705 (closed)

This MR does the following:

• Adds in editing mode a sidebar from which available visualizations can be selected.
• Clicking on one of the available visualizations creates a new dashboard with it.
• Adds a button that links to the visualization designer.
  • Note this does not have any save functionality right now!

This MR does not do the following:

• Resolve the issue where exiting edit mode won't undo changes. [Bug] Handle unsaved changes in analytics dashb... (#410349 - closed)
• Add the ability to remove panels once added. Add ability to remove panels in analytics dashb... (#410350 - closed)

Important to note that analytics dashboards is an experimental feature that is hidden behind a default off feature flag.

Screenshots or screen recordings

Before	After

How to set up and validate locally

Note: This feature has a lot of setup steps. If you need help please ask me or I can step through these during a call with you.

1. Follow these instructions to setup Product Analytics in GDK and configure a project.
2. Configure a custom dashboard project like in !112481 (merged).
   • This needs a repository with a main branch in the same group as your test project.
3. View the dashboard list at Project -> Analytics -> Dashboards.
4. Create a new dashboard by clicking on the New dashboard button.
5. Verify that you can add any of the available visualisations to the dashboard.
6. Verify that this can be saved.
7. Verify that clicking on the Create new visualization opens the designer.

How to add a custom visualization for testing.

Click to expand

Commit the following contents to .gitlab/dashboards/product_analytics/visualizations/new_custom_viz.yml to your main branch.

version: 1
type: ColumnChart
data:
  type: cube_analytics
  query:
    measures:
      - TrackedEvents.pageViewsCount
    dimensions:
      - TrackedEvents.parsedUaOsFamily
    limit: 100
    timezone: UTC
    filters: []
    timeDimensions: []
options:
  xAxis:
    name: Dimension
    type: category
  yAxis:
    name: Counts

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.