Move more logic in blockstore_processor behind allow_dead_slots flag … #3860

Job	Run time
android (ubuntu-20.04, x86_64-linux-android)	2m 47s
ios (macos-12, aarch64-apple-ios)	5m 18s
android (ubuntu-20.04, aarch64-linux-android)	2m 53s
ios (macos-12, x86_64-apple-ios)	6m 42s
android (ubuntu-20.04, i686-linux-android)	2m 49s
ios (macos-12, aarch64-apple-darwin)	4m 49s
ios (macos-12, x86_64-apple-darwin)	3m 34s
android (ubuntu-20.04, armv7-linux-androideabi)	3m 2s
error_reporting	0s
	31m 54s

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