feat(loadbalance): add loadbalancer using Alias Method to reduce the time complexity of weighted random load balancing algorithms

[nickxudotme]

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添加一种使用 Alias Method 的负载均衡方法，来减少权重随机负载均衡算法的时间复杂度

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:

Alias Method:

https://en.wikipedia.org/wiki/Alias_method
http://www.keithschwarz.com/darts-dice-coins/

zh(optional):

https://nickxu.me/post/darts-dice-coins-chinese-version

(Optional) Which issue(s) this PR fixes:

#1184

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a6d5d90) 66.89% compared to head (b2ff131) 66.97%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1199      +/-   ##
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+ Coverage    66.89%   66.97%   +0.07%     
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  Files          256      257       +1     
  Lines        19479    19534      +55     
===========================================
+ Hits         13031    13082      +51     
- Misses        5271     5282      +11     
+ Partials      1177     1170       -7     

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[ppzqh]

thanks for the contribution. Please fix the ci issue and add the reference of this algorithm in the pr description

[ppzqh]

Can we add a benchmark for init, which is also used when rebalance.

[nickxudotme]

BenchmarkAliasMethodPickerInit

goos: darwin
goarch: arm64
pkg: github.com/cloudwego/kitex/pkg/loadbalance
BenchmarkAliasMethodPickerInit
BenchmarkAliasMethodPickerInit/10ins
BenchmarkAliasMethodPickerInit/10ins-8         	 9356866	       136.7 ns/op	     400 B/op	       5 allocs/op
BenchmarkAliasMethodPickerInit/100ins
BenchmarkAliasMethodPickerInit/100ins-8        	 1512398	       848.7 ns/op	    4480 B/op	       5 allocs/op
BenchmarkAliasMethodPickerInit/1000ins
BenchmarkAliasMethodPickerInit/1000ins-8       	  180366	      6993 ns/op	   40960 B/op	       5 allocs/op
BenchmarkAliasMethodPickerInit/10000ins
BenchmarkAliasMethodPickerInit/10000ins-8      	   13801	     92550 ns/op	  409604 B/op	       5 allocs/op
PASS

[ppzqh]

LGTM

[nickxudotme]

我觉得这个 PR 已经可以和进去了（但是貌似会报一些我感觉奇怪的 CI 问题

[ppzqh]

我觉得这个 PR 已经可以和进去了（但是貌似会报一些我感觉奇怪的 CI 问题

什么问题？

[nickxudotme]

我觉得这个 PR 已经可以和进去了（但是貌似会报一些我感觉奇怪的 CI 问题

什么问题？

review 通过一下看看👀

[AsterDY]

kitex/pkg/loadbalance/weighted_balancer_test.go at 834c15a5e6c7def209f257246122803ed1e77b92 · cloudw 发现这个 BenchmarkWeightedPicker_Next 测试结果有点奇怪：“weitghted_random” 的性能并没有随着n增大而裂化（明明是O(N))，导致新算法的收益看起来不是很明显。初步debug看了下传到weightedRandomPicker.Next(）里面的instances一直都是10估计是有bug，cc @ppzqh 。 同学如果有兴趣也帮忙看看问题在哪吧 @NX-Official

[ppzqh]

这个单测问题我修了，辛苦rebase一下，再跑个测试

[jizhuozhi]

LGTM

[ppzqh]

@NX-Official Hi, 这个alis method的功能要辛苦你帮忙补充一个介绍文档。可以参考官网文档进行添加，包括中英文两个文件。感谢你的支持！
官网：https://www.cloudwego.io/zh/docs/kitex/tutorials/service-governance/loadbalance/