Replace all uses of the deprecated seastar::smp::count with
this_smp_shard_count() and smp::all_cpus() with this_smp_all_shards()
across the ScyllaDB codebase (seastar submodule untouched).
Both replacement functions require a reactor thread context. All call
sites were verified to run on reactor threads.
Notable cases:
- dht/token-sharding.hh: this_smp_shard_count() is used as a default
parameter value. This is safe since all callers are on reactor threads,
but the expression is now evaluated at each call site rather than being
a reference to a global variable.
- service/storage_service.hh, locator/abstract_replication_strategy.hh,
ent/encryption/encryption.cc: used in default member initializers and
constructor member-init-lists. Objects are always constructed on reactor
threads.
Not changed:
- scylla-gdb.py: reads smp::count as a GDB symbol (no reactor context).
- Python test files: only reference smp::count in comments/strings.