`RuntimeGenesiConfig`: json macro added #12034

Job	Run time
preflight / preflight	41s
preflight / ci-versions	1m 3s
check-runtime-migration (westend)	8m 43s
check-runtime-migration (asset-hub-westend)	6m 42s
check-runtime-migration (bridge-hub-westend)	5m 41s
check-runtime-migration (collectives-westend)	5m 56s
check-runtime-migration (coretime-westend)	6m 5s
All runtime migrations passed	1s
	34m 52s

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