Missing C API for CanKeysWithDifferentByteContentsBeEqual()

### Expected
Overriding CanKeysWithDifferentByteContentsBeEqual() fuction for custom comparator using C API

Which is needed for Hash Index

> Every comparator implementation should override this function and specify the behavior of the comparator. If a comparator can regard different keys equal, the function returns true, and as a result the hash index feature will not be enabled, and vice versa.

https://github.com/facebook/rocksdb/wiki/Data-Block-Hash-Index#things-that-need-attention

### Actual
Missing CanKeysWithDifferentByteContentsBeEqual() equivalent in C API