Add validator rpc call by modifying existing interface

[emailtovamos]

For now it is the easier way to implement what we want which involves:

1. Modify existing interface to add GetValidators() rpc end point
2. Add it in proto file and generate code
3. Add corresponding function in the client and server files
4. Save the client to be used by windower struct which calls the validators in its Delay() function
5. There might be better way to use the client

In future a new plugin can be created for the same functionality to follow SOLID better.

TODO: Make sure the validators are only gotten once a week either by code or by caching or by parallel/concurrent call