Expose LRU and blob cache options

[athre0z]

This PR exposes the following two DB options related to BlobDB caching:

https://github.com/facebook/rocksdb/blob/f6fd4b9dbd15dba36f7e5ad23de407b5c26b1460/include/rocksdb/advanced_options.h#L1129-L1148

[athre0z]

Added one more commit to also expose the advanced LRU cache constructor with custom options.

[aleksuss]

@athre0z overall looks good, but could you add some tests, please?

[zaidoon1]

This also LGTM, adding tests would be great

[athre0z]

I can write some tests, but it might take a while until I get to it depending on how deep these tests should go: I'm unfortunately rather short on time right now. Simply adding tests that invoke the new methods to make sure it links & doesn't segfault is quickly done, but I might have to read up a bit deeper if you'd like tests that actually make sure that RocksDB is caching things as expected etc (like some other test cases seem to do). What's the expectation here?

[zaidoon1]

I can write some tests, but it might take a while until I get to it depending on how deep these tests should go: I'm unfortunately rather short on time right now. Simply adding tests that invoke the new methods to make sure it links & doesn't segfault is quickly done, but I might have to read up a bit deeper if you'd like tests that actually make sure that RocksDB is caching things as expected etc (like some other test cases seem to do). What's the expectation here?

a simple test case where you set the new options being exposed here, and put some kvs without segfaulting is good enough