feat: specify an ovn underlay network through MicroOVN #1379

Job	Run time
Code	2m 13s
System (1.22.x, add)	27m 36s
System (1.22.x, instances)	24m 9s
System (1.22.x, basic)	27m 36s
System (1.22.x, recover)	16m 56s
System (1.22.x, interactive)	14m 2s
System (1.22.x, mismatch)	21m 5s
System (1.22.x, preseed)	21m 32s
documentation-checks / Run documentation checks	1m 14s
Trigger snap edge build	1s
	2h 36m 24s

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