vinyl: refactor compact helpers
vinyl: refactor compact helpers

Factor out pieces of code manipulating range->shadow and ->compact_list
to separate functions so that they could be reused on recovery vinyl
metadata from memtx.

mejedi/tarantool,mejedi/tarantool,mejedi/tarantool,rtsisyk/tarantool,mejedi/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,rtsisyk/tarantool