[BUGFIX] Stabilize ext:impexp acceptance tests

* Clickmenu needs to wait for full initialization
  before clicking on 'more'.
* Always wait for page elements when loading new page.

Resolves: #94875
Related: #94772
Releases: master
Change-Id: I883a0370c34309ca555076b4088f173d77579f61
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70549


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Alexander Nitsche <typo3@alexandernitsche.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Alexander Nitsche <typo3@alexandernitsche.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>