sstables: export filter memory size
sstables: export filter memory size

Signed-off-by: Glauber Costa <f8b79557d19b40666ebe336545a0b6178af65685@scylladb.com>

avikivity/scylla,capturePointer/scylla,duarten/scylla,scylladb/scylla,kangkot/scylla,duarten/scylla,phonkee/scylla,kjniemi/scylla,raphaelsc/scylla,avikivity/scylla,kangkot/scylla,scylladb/scylla,capturePointer/scylla,scylladb/scylla,phonkee/scylla,raphaelsc/scylla,kjniemi/scylla,raphaelsc/scylla,duarten/scylla,scylladb/scylla,senseb/scylla,capturePointer/scylla,avikivity/scylla,senseb/scylla,kjniemi/scylla,phonkee/scylla,kangkot/scylla,senseb/scylla