[BUGFIX] Improve SVG page tree

- drag and drop doesn't work on firefox
- when request returns error or 500 code loader is still visible
- loader isn't visible on start
- SVG tree page is duplicate on change left actions menu
- loader is duplicate on change left action menu
- nodes on drag & drop are too sensitive

Releases: master
Resolves: #83224
Resolves: #83176
Resolves: #83177

Change-Id: I03acf2244fe860b7fafd6067d8dfb31ef5bca064
Reviewed-on: https://review.typo3.org/54933


Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>