Remove obsolete types and methods.
Remove obsolete types and methods.

These types and methods are no longer in use since the index_reader is
now consuming promoted index incrementally.

Signed-off-by: Vladimir Krivopalov <dc9186a06078733915a6fcbab34e59120be2b484@scylladb.com>

scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,avikivity/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla