[TASK] Cleanup ext:viewpage template

There is no point in having the main template in
a sub folder, move it up. Additionally use full
EXT: syntax for f:translate arguments and avoid
a useless flashMessage VH call that is already
done by ModuleTemplate automatically.

Resolves: #96405
Releases: main
Change-Id: Id2f9e4bd28f9ed7649ff5b3c73348cf7d2307a51
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72747


Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>