lsa: Make reclamation on reserve refill more efficient
lsa: Make reclamation on reserve refill more efficient

Currently reserve refill allocates segments repeatedly until the
reserve threhsold is met. If single segment allocation needs to
reclaim memory, it will ask the reclaimer for one segment. The
reclaimer could make better decisions if it knew the total number of
segments we try to allocate. In particular, it would not attempt to
compact any segment until it evicts total amount of memory first,
which may reduce the total amount of segment compactions during
refill.

This patch changes refill to increase reclamation step used by
allocate_segment() so that it matches the total amount of memory we
refill.

avikivity/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,duarten/scylla