Monitor and optimize options for bloom filter

[acelyc111]

Feature Request

Describe the feature you'd like:

We use 10 bits per key for bloom filter, it provide 1% false positive rate, but some user might need a lower FP rate, like 0.1%. We need to do some benchmark on it to check whether it would introduce some unacceptable memory and disk space waste.
And also, we need to monitor more metrics of BF.
https://github.com/facebook/rocksdb/wiki/RocksDB-Bloom-Filter