This PR adds a filtering support. The filtering is done from the API server side (not from the source side). Source side filtering is a bit complicated to write an elegant solution, and we will handle it in the future (no optimization for alpha APIs).
We will also support limited types of columns for each API.
The API is as follows
ray list [resources] -- filter [key] [value] => filter data that's key==value.
In the future, we can also support more complicated filtering like !=, And, Or , or etc.