[BUGFIX] Use site name rather than pageUid for calling context menu

PageTree Acceptance tests must not rely on pageUids, as those can
change unexpected. Better to find the page via its title.

Credits to Christian Kuhn for coming up with the xpath.

Resolves: #93538
Releases: master, 10.4, 9.5
Change-Id: Ia6d887728bac05d775ecfc3a3cc45045f96ffd1f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67961


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>