tests: add logalloc_test for large contiguous allocations in a challenging environemnt
tests: add logalloc_test for large contiguous allocations in a challenging environemnt

Test large std allocations in an evironement that has seen many persistent
std allocations interspersed with lsa allocations, causing memory fragmentation.

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