feat(fqdn): Limit the cache size on dns_resolve

[GehaFearless]

The cache of dns_resolve is unlimited, the cache size may be huge.
Implement an expiration mechanism to limit the cache size and make
it possible to update the resolve result.

[acelyc111]

Good job!
Consider to use a LRU cache, thers is an implementation exported from RocksDB, see https://github.com/facebook/rocksdb/blob/main/include/rocksdb/cache.h#L270