Removed following properties of ColumnFamilyOptions, which have been deprecated for some time. (They cause issues with Cython right now, and will be obsolete in v7 anyway.)

* `soft_rate_limit`
* `hard_rate_limit`
* `rate_limit_delay_max_milliseconds`
* `purge_redundant_kvs_while_flush`
* `skip_log_error_on_recovery`

Remove unnecessary delete

Revert deleting Close method call

Add dependency to Cython in pyproject.toml file

Update tox configuration for unit test

Remove deprecated setup_requires