Threading fixes, MAVLink sequence number cleanup #3439

Job	Run time
Ubuntu/Debian packaging (Ubuntu 20.04)	10m 35s
ubuntu-20.04 (package, non-mavsdk_server)	6m 23s
coverage (ubuntu-20.04)	5m 13s
ubuntu-22.04 (package, non-mavsdk_server)	6m 0s
alpine 3.16.0 (musl)	19m 15s
android-arm	7m 1s
linux-armv6-musl	12m 4s
android-arm64	6m 28s
linux-armv6	5m 27s
linux-armv7l-musl	16m 16s
ios	5m 59s
android-x86	6m 17s
linux-armv7	5m 4s
linux-arm64-musl	13m 32s
ios_simulator	10m 59s
android-x86_64	6m 13s
linux-arm64	4m 53s
macOS	9m 2s
ubuntu-22.04 (check style and docs)	8m 21s
ubuntu-20.04 (non-mavsdk_server, non-superbuild)	5m 24s
macOS-framework	14m 55s
ubuntu-20.04 (mavsdk, hunter)	5m 9s
ubuntu-22.04 (proto check)	1m 21s
Windows	19m 30s
ubuntu-20.04 (mavsdk_server, superbuild)	12m 31s
ubuntu-22.04 (mavsdk_server, superbuild)	10m 2s
iOS XCFramework	53s
	3h 54m 47s

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