feat: specify an ovn underlay network through MicroOVN #1363

Job	Run time
System (1.22.x, add)	30m 37s
Code	1m 38s
System (1.22.x, instances)	29m 22s
System (1.22.x, basic)	29m 23s
System (1.22.x, recover)	19m 57s
System (1.22.x, interactive)	29m 20s
System (1.22.x, mismatch)	26m 38s
documentation-checks / Run documentation checks	1m 7s
System (1.22.x, preseed)	24m 58s
Trigger snap edge build	1s
	3h 13m 1s

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