Investigate UI cleanup

[mgiota]

Fixes #188582

This PR can be merged after this PR is merged and should be rebased with main.

This is how the UI looks like. It will be properly styled as part of the smaller subtasks defined in this ticket.

• Notes widget was moved on the sidebar
• A new "Add observation chart" button was added
• A few components were removed from the page like minitimeline, minimap, investigate_search_bar, investigate_detail (undo/redo), investigate_history

cc @kdelemme

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[mgiota]

I moved the InvestigateWidgetGrid to the sidebar, so that added notes appear on the sidebar.

TODO: Once we add the other widgets (ESQL, embeddable) in the UI, we need to rethink the InvestigateWidgetGrid, because now all widgets (included notes) appear in one common timeline. That's not what we want in the mock up design

[mgiota]

Update
Here's the visual state of current PR

There is no design applied to the UI yet. It brings the investigate-app from this POC with a few components deleted. Goal of this PR is to have the investigate-app being merged, so that more people can start working on the smaller tasks defined here.