Previously the first activeChanged signal got lost because it was not connected yet to the LinkInterface which resulted in a link incorrectly shown as inactive.

Show the link indicator in the tool bar if two or more links are connected and at least one of them is a high latency link.
Show in the link indicator if a link is inactive.

- Improve function names
- For notifications of an active link change only show the priority keyword if multiple links are connected
- Use QMap instead of QList for the HeartbeatTimers
- Style improvements
- Simplify sending the MAV_CMD_CONTROL_HIGH_LATENCY command

Add the HeartbeatTimer class to track a single heartbeat for a single link.
For every new received heartbeat an instance of the class is created.
Every instance emits a signal if it timed out or the timer is restarted.
Each vehicle then decides based on all different signals which link is the
priority link.

Each link updates the active property based on incoming bytes.
The vehicle tracks the active property of each link and in case of an inactive priority link it updates the priority link.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Work around a new Windows issue where the call to list the local network interfaces takes for freaking ever to return, blocking the UDP thread altogether.

Maintain a list of address/port pairs instead of a address/port map.

* Flight modes still not implemented. Waiting on message change.
* Also includes various cauterization of UI things which should not be
available on high latency link.

This ensures no ports are being displayed to the user that are definitely unusable.

The earlier sleep calls disabled the app event queue, leading to "beachballing" in Mac OS and a visible boot delay / jitter. Running the event loop actively while waiting prevents the UI from freezing.

We were connecting to system peripherals before, which adds boot delay as QGC re-tries opening the port. We were also opening serial ports two times on Mac OS: Once as /dev/cu.usbmodem1 and once as /dev/tty.usbmodem1 - since the cu.usbmodem alias was already open, the 2nd opening always failed, leading to further boot delay.