Improve dashboards layout customization

[paolodamico]

Is your feature request related to a problem? & Describe the solution you'd like

We could improve the experience for customizing dashboards. By default you wouldn't expect to edit dashboards every time (editing should be the exception). As such, we could restructure the way the "lock mode" works to instead be something like "build mode". A user reported the layout even changing between sessions.

In addition to the above, we need to make sure any layouts scale property to smaller resolutions.

Finally worth noting is that we currently allow dragging/dropping dashboards to almost any position in the screen. We should enforce a grid-like constraint in which you can only add graphs which are properly aligned.

Describe alternatives you've considered

Keep it as is, maybe default to lock mode?

Additional context

From a customer call.

Thank you for your feature request – we love each and every one!

[paolodamico]

Closing in favor of #4312