feat: port demuxer and app to cmake #308

Job	Run time
Settings / settings	1s
Lint / Lint	14s
Build and test / Matrix configuration	7s
Test Linux distros / Matrix configuration	7s
Build docs / Build docs	35s
Official Docker image / Build	50s
Build and test / linux x64 Debug static	12m 36s
Build and test / linux x64 Debug shared	15m 37s
Build and test / linux x64 Release static	17m 48s
Build and test / linux x64 Release shared	15m 18s
Build and test / osx x64 Debug static	13m 36s
Build and test / osx x64 Debug shared	14m 18s
Build and test / osx x64 Release static	16m 49s
Build and test / osx x64 Release shared	16m 40s
Build and test / win x64 Debug static	19m 14s
Build and test / win x64 Debug shared	18m 23s
Build and test / win x64 Release static	33m 30s
Build and test / win x64 Release shared	24m 12s
Build and test / linux arm64 Debug static	19m 41s
Build and test / linux arm64 Debug shared	20m 9s
Build and test / linux arm64 Release static	20m 39s
Build and test / linux arm64 Release shared	20m 32s
Test Linux distros / Alpine	16m 5s
Test Linux distros / ArchLinux	21m 40s
Test Linux distros / CentOS	14m 52s
Test Linux distros / Debian	14m 22s
Test Linux distros / Fedora	14m 13s
Test Linux distros / OpenSUSE	14m 19s
Test Linux distros / Ubuntu	14m 26s
	6h 50m 53s

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