When using 'Send a file/URL' in the indicator with multiple devices, the
device the user selects for file sharing is not automatically selected in
the URL handler dialog that follows.
This happens because `model.rowForDevice(deviceId)` is called without
waiting for the model to be populated, always returning -1.
Resolving this exposed another bug, where the selected device was still
not the one picked. This happens because `proxyModel` is used to fill the
`QComboBox` but `model` is used to find the correct index. Since
`DevicesPluginFilterProxyModel` sorts and filters the data from `model`
the indices do not match.
This commit addresses these issues by deferring the device selection until
data is available and implementing `rowForDevice` for filtered/sorted data
in `DevicesPluginFilterProxyModel`.
The rationale is explained in https://planet.kde.org/friedrich-kossebau-2023-06-28-include-also-moc-files-of-headers/
In case of KDEConnect, it impressively speeds up compilation. Before it
took 390 seconds on a clean build and with this change it took 330 seconds.
This is due to the mocs_compilation having to include the header files
and thus all their headers. Due to the lots of small plugins we have,
this means that the same headers must be compiled plenty of times.
When we include the moc files directly in the C++ file, they are already
available.
