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.
Closesscylladb/scylladb#20186
* github.com:scylladb/scylladb:
perf/perf_sstable: add {crawling,partitioned}_streaming modes
test/perf/perf_sstable: use switch-case when appropriate