Add some application container documentation #2859

Job	Run time
Code (oldstable)	7m 36s
Client (oldstable, ubuntu-latest)	1m 2s
Code (stable)	7m 33s
Client (oldstable, macos-latest)	53s
Documentation	3m 43s
Code (tip)	10m 19s
Client (oldstable, windows-latest)	2m 19s
System (stable, cluster, dir)	11m 35s
Client (stable, ubuntu-latest)	1m 7s
System (stable, cluster, btrfs)	12m 8s
Client (stable, macos-latest)	56s
System (stable, cluster, lvm)	12m 36s
Client (stable, windows-latest)	1m 25s
System (stable, cluster, zfs)	12m 28s
System (stable, cluster, ceph)	15m 50s
System (stable, cluster, random)	12m 56s
System (stable, standalone, dir)	22m 19s
System (stable, standalone, btrfs)	22m 43s
System (stable, standalone, lvm)	39m 49s
System (stable, standalone, zfs)	38m 11s
System (stable, standalone, ceph)	1h 15m 0s
System (stable, standalone, random)	23m 14s
System (oldstable, cluster, dir)	11m 47s
System (oldstable, standalone, dir)	21m 59s
System (tip, cluster, dir)	14m 32s
System (tip, standalone, dir)	24m 52s
	6h 48m 52s

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