WindowClone: Layout in allocate virtual

[leolost2605]

Currently we are doing most of the layout management by hardcoding x, y, width and height of our child actors. However we can make the whole thing simpler and more robust by doing the layout management in the allocate virtual method as recommended by clutter docs.

Since the root cause for the following issues was that we didn't allocate some children on rare occasions which was fixed in this PR this
fixes #2053 and
fixes #1898 and therefore
closes #2072

There are still some issues when windows spawn while multitasking view is open (like for example they reserve space but don't show) that I would like to tackle in follow up PRs but at least it doesn't completely break anymore as on current main :)

fixes #2088

[danirabbit]

I can confirm that this fixes the linked issues, but it looks like the textures (window clones, close buttons, app icons) are all rendered half a pixel offset so they're blurry (this is on LoDPI and Wayland)

[danirabbit]

Tooltips also appear to be cut off and text looks pretty gnarly. Although when I went back to get a screenshot the other textures all look aligned correctly here 🤔

This branch:

main:

[leolost2605]

@danirabbit the allocations are clamped to pixels now could you try again with that? I'm not so good at noticing those differences 😅
(and the tooltip thing I don't seem to be able to reproduce, probably requires a very specific window size and name 🤷)