Migrate forach/Q_FOREACH as C++11 is assumed to be min for codebase

[DominiqueFuchs]

Search shows ~90 foreach/Q_FOREACH uses throughout the code. TODO. As @er-vin pointed out in a recent PR, the Qt variant is deprecated now where compact and efficient std alternatives are present. Also, in some cases probably more efficient/safe.

[snake66]

I'd like to have a look at this if nobody minds.

[er-vin]

Sure go ahead, it's likely a clazy run away. :-)

[joshtrichards]

Context:

• https://doc.qt.io/qt-6/foreach-keyword.html
• https://doc.qt.io/qt-6.5/qforeach-qtcore-proxy.html

Though in these newer versions of the docs, they seem to have downplayed from deprecated to "try not to use".

Looks like some of these were eliminated via #2272, but more remain:

https://github.com/search?q=repo%3Anextcloud%2Fdesktop%20foreach&type=code