Add infrastructure for OVN events #2916

Job	Run time
Documentation	5m 4s
Code (oldstable)	3m 55s
Client (oldstable, ubuntu-latest)	59s
Code (stable)	4m 8s
System (stable, cluster, dir)	11m 56s
Client (oldstable, macos-latest)	54s
System (stable, cluster, btrfs)	12m 3s
Code (tip)	6m 24s
Client (oldstable, windows-latest)	2m 20s
System (stable, cluster, lvm)	12m 46s
Client (stable, ubuntu-latest)	1m 7s
Client (stable, macos-latest)	57s
System (stable, cluster, zfs)	12m 10s
Client (stable, windows-latest)	1m 33s
System (stable, cluster, ceph)	17m 37s
System (stable, cluster, random)	12m 49s
System (stable, standalone, dir)	22m 20s
System (stable, standalone, btrfs)	22m 7s
System (stable, standalone, lvm)	26m 42s
System (stable, standalone, zfs)	26m 40s
System (stable, standalone, ceph)	26m 42s
System (stable, standalone, random)	24m 51s
System (oldstable, cluster, dir)	11m 46s
System (oldstable, standalone, dir)	22m 12s
System (tip, cluster, dir)	14m 27s
System (tip, standalone, dir)	25m 26s
	5h 29m 55s

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