Storage integration tests: restructure to attempt to mitigate flakes #5113

Job	Run time
pod-lib-lint (ios, macos-12)	4m 59s
pod-lib-lint (ios, macos-13)	8m 24s
quickstart (macos-12, Xcode_14.2)	9m 51s
pod-lib-lint (tvos, macos-12)	3m 43s
quickstart (macos-13, Xcode_15.1)	8m 25s
pod-lib-lint (tvos, macos-13)	5m 28s
pod-lib-lint (macos, macos-12)	3m 49s
quickstart-ftl-cron-only	0s
pod-lib-lint (macos, macos-13)	5m 13s
pod-lib-lint (watchos, macos-12)	2m 58s
pod-lib-lint (watchos, macos-13)	4m 19s
spm (macos-12, Xcode_14.2)	5m 31s
spm (macos-13, Xcode_15.1)	6m 38s
spm-cron	0s
storage-integration-tests (macos-13, Xcode_15.1, Swift, ObjC)	2m 18s
storage-cron-only	1s
	1h 11m 37s

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