tests: memtable_test: Add test for concurrent reading and schema changes
tests: memtable_test: Add test for concurrent reading and schema changes

raphaelsc/scylla,raphaelsc/scylla,kjniemi/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,duarten/scylla,scylladb/scylla,duarten/scylla,kjniemi/scylla,kjniemi/scylla,avikivity/scylla,raphaelsc/scylla,scylladb/scylla,avikivity/scylla