for testing the load performance of load_and_stream operation. Refs #19989 --- no need to backport. it adds two new tests to the existing `perf_sstable` tool for evaluating the load performance when performing the "load_and_streaming" operation. hence has no impact on the production. Closes scylladb/scylladb#20186 * github.com:scylladb/scylladb: perf/perf_sstable: add {crawling,partitioned}_streaming modes test/perf/perf_sstable: use switch-case when appropriate