The memory usage is tracked with the help of a semaphore, so just export
its "consumed" units.
One tricky place here is the need to skip metrics registration for
scylla-sstable tool. The thing is that the tools starts the storage
manager and sstables manager on start and then some of tool's operations
may want to start both managers again (via cql environment) causing
double metrics registration exception.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closesscylladb/scylladb#25769
b26816f80d