Port from qAsConst() to std::as_const()

We've been requiring C++17 since Qt 6.0, and our qAsConst use finally
starts to bother us (QTBUG-99313), so time to port away from it
now.

Since qAsConst has exactly the same semantics as std::as_const (down
to rvalue treatment, constexpr'ness and noexcept'ness), there's really
nothing more to it than a global search-and-replace.

Task-number: QTBUG-99313
Change-Id: I88edd91395849574436299b8badda21bb93bea39
Reviewed-by: hjk <hjk@qt.io>

src/plugins/fakevim/fakevimhandler.cpp

@@ -6122,7 +6122,7 @@ bool FakeVimHandler::Private::handleExRegisterCommand(const ExCommand &cmd)
     }
     QString info;
     info += "--- Registers ---\n";
-    for (char reg : qAsConst(regs)) {
+    for (char reg : std::as_const(regs)) {
         QString value = quoteUnprintable(registerContents(reg));
         info += QString("\"%1   %2\n").arg(reg).arg(value);
     }
@@ -6528,7 +6528,7 @@ bool FakeVimHandler::Private::handleExMultiRepeatCommand(const ExCommand &cmd)
 
     beginEditBlock();
 
-    for (const QTextCursor &tc : qAsConst(matches)) {
+    for (const QTextCursor &tc : std::as_const(matches)) {
         setPosition(tc.position());
         handleExCommand(innerCmd);
     }