Page tree will fetch just 2 levels of pages plus pages which
are expanded on the initial load.
Next levels are fetched on demand via Ajax when expanding the node.
Search works server side now. To clear search, click on "x"
button.

Change-Id: I2691c531b419398325989070c375a9ec0d08ae82
Releases: master, 10.4, 9.5
Resolves: #88943
Resolves: #88098
Resolves: #88259
Resolves: #91884
Resolves: #91753
Resolves: #91916
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65208


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Riny van Tiggelen <info@online-gamer.nl>
Tested-by: Uwe Trotzek <trotzek@citeq.de>
Tested-by: Marcus Schwemer <ms@schwemer.de>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Marcus Schwemer <ms@schwemer.de>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>