chore(cli): create 'gateway' subcommand for network commands #2104

Job	Run time
integration (kong:1.4.3)	2m 19s
integration (kong:1.5.1)	1m 52s
integration (kong:2.0.5)	1m 46s
integration (kong:2.1.4)	1m 44s
integration (kong:2.2.2)	2m 2s
integration (kong:2.3.3)	2m 7s
integration (kong:2.4.1)	1m 51s
integration (kong:2.5.1)	2m 21s
integration (kong:2.6.0)	1m 52s
integration (kong:2.7)	1m 43s
integration (kong:2.8)	2m 12s
integration (kong:3.0)	2m 16s
integration (kong:3.1)	2m 3s
integration (kong:3.2)	1m 56s
integration (kong:3.3)	2m 2s
integration (kong/kong:master-alpine)	1m 49s
	31m 55s

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