Reduce large allocations and reactor stalls seen in #11005
by open coding `get_address_ranges` and using std::vector::insert
to efficiently appending the ranges returned by `get_primary_ranges_for`
onto the returned token_range_vector in contrast to building
an unordered_multimap<inet_address, dht::token_range> first in
`get_address_ranges` and traversing it and adding one token_range
at a time.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
1d4aea4441