Add infrastructure for OVN events #2917

Job	Run time
Documentation	5m 30s
Code (oldstable)	7m 30s
Client (oldstable, ubuntu-latest)	58s
System (stable, cluster, dir)	12m 8s
Code (stable)	7m 27s
Client (oldstable, macos-latest)	53s
System (stable, cluster, btrfs)	14m 48s
Code (tip)	10m 5s
Client (oldstable, windows-latest)	2m 27s
System (stable, cluster, lvm)	13m 9s
Client (stable, ubuntu-latest)	1m 6s
System (stable, cluster, zfs)	13m 43s
Client (stable, macos-latest)	56s
System (stable, cluster, ceph)	15m 57s
System (stable, cluster, random)	11m 55s
Client (stable, windows-latest)	1m 24s
System (stable, standalone, dir)	22m 17s
System (stable, standalone, btrfs)	22m 6s
System (stable, standalone, lvm)	39m 20s
System (stable, standalone, zfs)	39m 48s
System (stable, standalone, ceph)	1h 15m 53s
System (stable, standalone, random)	23m 44s
System (oldstable, cluster, dir)	11m 42s
System (oldstable, standalone, dir)	22m 17s
System (tip, cluster, dir)	14m 27s
System (tip, standalone, dir)	25m 12s
	6h 56m 42s

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