consistent hash load balance

[imxyb]

Signed-off-by: imxyb [email protected]

What this PR does:
add consistent hash load balance
Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

Merging #261 into master will decrease coverage by 0.65%.
The diff coverage is 91.17%.

@@            Coverage Diff             @@
##           master     #261      +/-   ##
==========================================
- Coverage   65.78%   65.13%   -0.66%     
==========================================
  Files         105      106       +1     
  Lines        6792     6860      +68     
==========================================
  Hits         4468     4468              
- Misses       1876     1944      +68     
  Partials      448      448

Impacted Files	Coverage Δ
cluster/loadbalance/consistent_hash.go	91.17% <91.17%> (ø)
cluster/cluster_impl/base_cluster_invoker.go	54.71% <0%> (-16.99%)	⬇️
protocol/dubbo/pool.go	57.86% <0%> (-15.74%)	⬇️
protocol/dubbo/listener.go	51.19% <0%> (-10.72%)	⬇️
protocol/dubbo/codec.go	76.47% <0%> (-5.89%)	⬇️
protocol/dubbo/readwriter.go	67.9% <0%> (-2.47%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 78e7ed0...80e5bf5. Read the comment docs.

[imxyb]

@fangyincheng @zouyx @hxmhlt PTAL

[fangyincheng]

LGTM

[AlexStocks]

LGTM