New filter plugin: logstash-filter-memoize

I want contribute to [logstash-plugins](https://github.com/logstash-plugins) my new filter plugin [`logstash-filter-memoize`](https://github.com/sw-jung/logstash-filter-memoize).

This filter can provides memoization to any filter.

See #8530 to show history of this plugin

### Example of usage

```ruby
filter {
memoize {
key => "%{host}"
fields => ["host_owner", "host_location"]
filter_name => "elasticsearch"
filter_options => {
query => "host:%{host}"
index => "known_host"
fields => {
"host_owner" => "host_owner"
"host_location" => "host_location"
}
}
}
}
```

### Links

- github: https://github.com/sw-jung/logstash-filter-memoize
- rubygems: https://rubygems.org/gems/logstash-filter-memoize