[4.0] Eliminating cpanel jumping

[Fedik]

Pull Request for Issue # .

Summary of Changes

The patch should eliminate cpanel jumping, or at least reduce it much.
I have delayed all AJAX request to wait until the content is rendered.
And improved MasonryLayout calculation a bit.

Testing Instructions

Apply patch. Run npm install.
Visit backend Dashboard and System section.

Actual result BEFORE applying this Pull Request

Notice that "Update Checks" runs immediately.
And cpanel boxes jumps a bit.

Expected result AFTER applying this Pull Request

"Update Checks" runs with a delay, only after the page is loaded.
And cpanel boxes does not jump.

Documentation Changes Required

nope

[brianteeman]

I have tested this item ✅ successfully on bf0a8cc

works great!!
tested all dashboards with and without sidemenu

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[richard67]

I have tested this item ✅ successfully on bf0a8cc

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/35069.}

[richard67]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/35069.}

[wilsonge]

Thanks!