[Feature Request] implement RPC endpoints to stop and start sources

[ryn9]

Is your feature request related to a problem? Please describe.

It would be helpful to have start and stop RPC endpoints for controlling sources from outside fluentd. For example - if we have an external monitoring script - we could halt input using dynamic factors and resume input when appropriate.

Describe the solution you'd like

implement RPC endpoints to stop and start sources

This was part of the original idea of implementing RPC endpoints.

See: https://github.com/fluent/fluentd/issues/575 https://github.com/fluent/fluentd/pull/585

Describe alternatives you've considered

N/A

Additional context

N/A