Forward plugin: Add dynamic loadbalancing algorithms

[hawwwdi]

What would you like to be added:
Currently, the forward plugin offers only two static load balancing algorithms: round robin and sequential. I propose the integration of dynamic algorithms, such as load balancing based on the response time of upstream DNS servers.
Why is this needed:
In my setup, I've configured three upstream DNS servers in the forward plugin, utilizing the sequential load balancing algorithm. However, when the latency of upstream server A increases, it impacts the entire Kubernetes cluster by elongating the time taken for name resolution when establishing new connections to certain hosts. I advocate for the inclusion of dynamic load balancing algorithms within the forward plugin to address this issue. Utilizing metrics like ResponseTime - QueryTime or something akin to the coredns_forward_request_duration_seconds metric could facilitate the implementation of a dynamic load balancing strategy. This would mitigate the adverse effects caused by latency spikes in individual upstream servers, ensuring smoother operation of the Kubernetes cluster.