Add validations for namespaced storage layout (#876) #959

Job	Run time
coverage	8m 58s
lint	1m 49s
tests (core)	1m 51s
tests (plugin-hardhat)	6m 4s
tests (plugin-truffle)	2m 19s
tests (plugin-defender-hardhat)	7m 1s
	28m 2s

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