index_entry.hh (the current home of `promoted_index_blocks_reader`) is included in `sstables.hh` and thus in half our code-base. All that code really doesn't need the definition of the promoted index blocks reader which also pulls in the sstables parser mechanism. Move it into its own header and only include it where it is actually needed: the promoted index cursor implementations. Signed-off-by: Botond Dénes <bdenes@scylladb.com> Message-Id: <20210317093654.34196-1-bdenes@scylladb.com>