[Infra] Update storage workflow to use macOS 15 for Xcode 16 jobs #5709

Job	Run time
storage-integration-tests (Swift)	19m 0s
storage-integration-tests (ObjC)	7m 51s
quickstart (swift, macos-14, Xcode_15.3)	3m 45s
spm-package-resolved	1m 17s
pod-lib-lint (ios, macos-14)	3m 5s
pod-lib-lint (tvos, macos-14)	2m 41s
quickstart-ftl-cron-only	0s
pod-lib-lint (macos, macos-14)	2m 22s
pod-lib-lint (watchos, macos-14)	2m 10s
pod-lib-lint (macos-15, Xcode_16.1, --test-specs=unit)	9m 44s
spm (macos-13, Xcode_15.2, iOS)	8m 2s
spm (macos-14, Xcode_15.4, iOS)	16m 20s
spm (macos-15, Xcode_16.1, iOS)	2m 20s
spm (macos-15, Xcode_16.1, tvOS)	1m 51s
spm (macos-15, Xcode_16.1, macOS)	2m 12s
spm (macos-15, Xcode_16.1, watchOS)	2m 12s
spm (macos-15, Xcode_16.1, catalyst)	2m 0s
spm (macos-15, Xcode_16.1, visionOS)	2m 21s
storage-cron-only	0s
	1h 29m 13s

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