One version returns only the ranges
std::vector<range<token>>
Another version returns a map
std::unordered_map<range<token>, std::unordered_set<inet_address>>
which is converted from
std::unordered_multimap<range<token>, inet_address>
They are needed by token_metadata::pending_endpoints_for,
storage_service::get_all_ranges_with_strict_sources_for and
storage_service::decommission.
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