chore: switch from cosmos-sdk/network to testnode package (#3118) #6612

Job	Run time
docker-security-build / prepare-env	5s
docker-txsim-build / prepare-env	2s
docker-txsim-build / logic-check	1s
docker-security-build / logic-check	1s
docker-txsim-build / docker-security	1m 53s
docker-security-build / docker-security	1m 51s
docker-txsim-build / docker-build (DockerHub; docker.io/celestiaorg/txsim)	4m 14s
docker-txsim-build / docker-build (GHCR; ghcr.io/celestiaorg/txsim)	3m 54s
docker-txsim-build / docker-build (ScaleWay; rg.fr-par.scw.cloud/celestiaorg/txsim)	4m 9s
docker-security-build / docker-build (DockerHub; docker.io/celestiaorg/celestia-app)	2m 54s
docker-security-build / docker-build (GHCR; ghcr.io/celestiaorg/celestia-app)	3m 8s
docker-security-build / docker-build (ScaleWay; rg.fr-par.scw.cloud/celestiaorg/celestia-app)	3m 20s
	25m 32s

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