Fix selection issues

[gbalint]

Problem:

1. In a selected scene, dragging an element should drag the scene not the element

2. In a selected scene, clicking on an element should select the element

3. In a selected scene, dragging an element under the threshold not move anything, but select the element

4. In a selected scene, cmd-dragging an element should drag the element not the scene

5. In a selected scene, cmd-clicking an element should select the element

6. In a selected scene, cmd-dragging an element under the drag threshold should not move anything, but select the element

Fix:
To fix 1-2-3 we need to make sure that dragging below the threshold is handled as a "click", so the selection happens on mouse up.

To fix 4-5-6 we need to make sure the cmd-mousedown already selects the element, which guarantees that the following dragging operates on the element (and not the scene)

Meanwhile, the failing tests uncovered that we have an extra bug: you can deselect a selected item if you click on a non-visible (e.g. cropped) part of it. To fix it I modified the behavior of findValidTarget in dont-prefer-selected mode: it means we should change our selection to something different if possible, but we should still not deselect it. To make this clearer I renamed don't-prefer-selected to prefer-more-specific-selection

As I fixed the tests I had to realize that our dragging helper functions are not good enough: we can specifiy modifier keys, but we can not specify separate modifier keys for the mouse down and for the mouse move events. Which is necessary because e.g. cmd changes the behavior differently in the two cases: cmd on mouse down changes how selection work, so it changes what will be dragged, while cmd on mouse move changes which strategy will be applied (cmd allows reparenting).

Manual Tests:
I hereby swear that:

• I opened a hydrogen project and it loaded
• I could navigate to various routes in Preview mode

Fixes #6012

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[relativeci]

#13559 Bundle Size — 62.65MiB (~+0.01%).

6d893a9(current) vs 6339ece master#13540(baseline)

Warning

Bundle contains 70 duplicate packages – View duplicate packages

Bundle metrics   2 changes 1 regression

	Current #13559	Baseline #13540
Initial JS	45.72MiB(~+0.01%)	45.72MiB
Initial CSS	0B	0B
Cache Invalidation	21.57%	21.55%
Chunks	31	31
Assets	34	34
Modules	4380	4380
Duplicate Modules	525	525
Duplicate Code	31.64%	31.64%
Packages	469	469
Duplicate Packages	70	70

Bundle size by type   2 changes 1 regression 1 improvement

	Current #13559	Baseline #13540
JS	62.64MiB (~+0.01%)	62.64MiB
HTML	11.16KiB (-0.33%)	11.2KiB

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