feat(loadbalance): do not cache all the keys for Consistent Hash

[DMwangnima]

What type of PR is this?

feat

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• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

(Optional) Translate the PR title into Chinese.

feat: 对于一致性哈希，不缓存所有的键

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

en:
Consistent hashing caches all the Keys, which in a scenario where the Keys are very fragmented, may cause a constant increase in memory and increase the overhead of managing the cache, thus affecting performance.
zh(optional):
一致性哈希会缓存所有的 Key, 在 Key 非常分散的场景下，可能会造成内存的持续升高以及增大管理缓存的开销，进而影响性能

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

(optional) The PR that updates user documentation:

[DMwangnima]

Key Characteristic

Random Key with length of 30.
Generate Func:

func getRandomString(length int) string {
	var resBuilder strings.Builder
	resBuilder.Grow(length)
	corpus := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	rand.Seed(time.Now().UnixNano() + int64(100))
	for i := 0; i < length; i++ {
		resBuilder.WriteByte(corpus[rand.Intn(len(corpus))])
	}
	return resBuilder.String()
}

Benchmark Result:

• New version (without cache)

BenchmarkConsistPicker_RandomDistributionKey
BenchmarkConsistPicker_RandomDistributionKey/10ins
BenchmarkConsistPicker_RandomDistributionKey/10ins-12         	 2417481	       508.9 ns/op	      48 B/op	       1 allocs/op
BenchmarkConsistPicker_RandomDistributionKey/100ins
BenchmarkConsistPicker_RandomDistributionKey/100ins-12        	 2140726	       534.6 ns/op	      48 B/op	       1 allocs/op
BenchmarkConsistPicker_RandomDistributionKey/1000ins
BenchmarkConsistPicker_RandomDistributionKey/1000ins-12       	 2848216	       407.7 ns/op	      48 B/op	       1 allocs/op
BenchmarkConsistPicker_RandomDistributionKey/10000ins
BenchmarkConsistPicker_RandomDistributionKey/10000ins-12      	 2701766	       492.7 ns/op	      48 B/op	       1 allocs/op

• Old version (with cache)

BenchmarkConsistPicker_RandomDistributionKey
BenchmarkConsistPicker_RandomDistributionKey/10ins
BenchmarkConsistPicker_RandomDistributionKey/10ins-12         	  671974	      1959 ns/op	     363 B/op	       9 allocs/op
BenchmarkConsistPicker_RandomDistributionKey/100ins
BenchmarkConsistPicker_RandomDistributionKey/100ins-12        	  568735	      2182 ns/op	     379 B/op	       9 allocs/op
BenchmarkConsistPicker_RandomDistributionKey/1000ins
BenchmarkConsistPicker_RandomDistributionKey/1000ins-12       	  576940	      2358 ns/op	     486 B/op	       9 allocs/op
BenchmarkConsistPicker_RandomDistributionKey/10000ins
BenchmarkConsistPicker_RandomDistributionKey/10000ins-12      	  475820	      2702 ns/op	     515 B/op	       9 allocs/op