The watchdog was used in a few places as a shortcut to skip reading
data. Further, it was used in some places in the UI to display
connectivity. But it also introduced quite some complexity. In some
cases it can be fragile: network accessibilty cannot be looked up on all
platforms/hardware constellations. The connectivity could change
between the last watchdog call and the real call. Hence all readers must
still handle the case where the connection fails.
To simplify swift and further reduce the dependency onto the project
infrastructure (pings etc.), this removes the watchdog.
This also removes the QNetworkConfigurationManager, which is deprecated
and not available with Qt6.
Rational: Normally calling synchronize multiple times does not matter. However, it can time out if the cache is in use (e.g. saving) and create an exception. This exception is just unwanted "noise".
* multi format compatible (automatically detect format)
* flag if cache values shall be overridden
* init from resource files (those are the files coming with the installer)
* automatically read in background if reader is (already) in its own thread (otherwise cache.set() ASSERT)
* added getAirlineIcaoCodeForUniqueDesignatorOrDefault and getAirlineIcaoCodeForUniqueIataCodeOrDefault from reader/web data services
* rearranged order of functions in ICAO reader
* added some more functions like "containsXX" in reader
* in case the internet provider is down, this is not detected
* extended test to detect if access is possible
* in case of downtime this indicated in status component
* use doWorkCheck
* relaxed doWorkCheck in unit tests
* removed isShuttingDown, gracefulShutdown
* set timer object name (in case something is wrong, we might see the name in the log)
* now ignore incomplete entities for airline/aircraft ICAOs from DB
* utility functions to find invalid designators
* adjusted unit test, avoid taking a random element
* and fixed 4 wrong ICAO entries in DB
* new read state "skipped"
* renamed to "isNetworkConnectedAndAccessible"
* checking before reading, which would only fail if network is not accessible
* added amit functions in readers
* cacheHasChanged functions (needed because data of caches are loaded in background)
* pinned small caches
* CDatabaseReader::readInBackgroundThread uses admitCaches now
