Provide wrappers for WriteBatchWithIndex functions in the speedb rust interface

[speedbmike]

WriteBatchWithIndex is exposed in the RocksDB/Speedb C interface, but no wrappers are available in Rust.
There is an issue in rust-rocksdb (836), but it doesn't seem to be active.

The C interface for WriteBatchWithIndex is available in c.h, but there isn't a test or usage example for many of the functions (some are available in c_test.c, others are only defined and never used anywhere).

So in the first stage this interface should be validated and then a wrapper should be written in rust-speedb project.

The full list of functions:
rocksdb_writebatch_wi_destroy
rocksdb_writebatch_wi_clear
rocksdb_writebatch_wi_count
rocksdb_writebatch_wi_put
rocksdb_writebatch_wi_put_cf
rocksdb_writebatch_wi_putv
rocksdb_writebatch_wi_putv_cf
rocksdb_writebatch_wi_merge
rocksdb_writebatch_wi_merge_cf
rocksdb_writebatch_wi_mergev
rocksdb_writebatch_wi_mergev_cf
rocksdb_writebatch_wi_delete
rocksdb_writebatch_wi_singledelete
rocksdb_writebatch_wi_delete_cf
rocksdb_writebatch_wi_singledelete_cf
rocksdb_writebatch_wi_deletev
rocksdb_writebatch_wi_deletev_cf
rocksdb_writebatch_wi_delete_range
rocksdb_writebatch_wi_delete_range_cf
rocksdb_writebatch_wi_delete_rangev
rocksdb_writebatch_wi_delete_rangev_cf
rocksdb_writebatch_wi_put_log_data
rocksdb_writebatch_wi_iterate
rocksdb_writebatch_wi_data
rocksdb_writebatch_wi_set_save_point
rocksdb_writebatch_wi_rollback_to_save_point
rocksdb_writebatch_wi_get_from_batch
rocksdb_writebatch_wi_get_from_batch_cf
rocksdb_writebatch_wi_get_from_batch_and_db
rocksdb_writebatch_wi_get_from_batch_and_db_cf