rm some pkgs

v2.6.5

rm pkgs that depend on xxhash v1

copy from caddyserver

reverseproxy: weighted_round_robin load balancing policy (#5579)

* added weighted round robin algorithm to load balancer

* added an adapt integration test for wrr and fixed a typo

* changed args format to Caddyfile args convention

* added provisioner and validator for wrr

* simplified the code and improved doc