[#3860] Optimize gray routing rule algorithm

[chengyouling]

No description provided.

[codecov-commenter]

Codecov Report

Merging #3862 (9194c44) into master (554e4e2) will increase coverage by 0.02%.
The diff coverage is 0.00%.

❗ Current head 9194c44 differs from pull request most recent head f2a10f5. Consider uploading reports for the commit f2a10f5 to get more accurate results

@@             Coverage Diff              @@
##             master    #3862      +/-   ##
============================================
+ Coverage     43.98%   44.01%   +0.02%     
+ Complexity     6088     6087       -1     
============================================
  Files          1557     1557              
  Lines         38288    38262      -26     
  Branches       3513     3506       -7     
============================================
  Hits          16841    16841              
+ Misses        20136    20112      -24     
+ Partials       1311     1309       -2     

Impacted Files	Coverage Δ
...b/router/distribute/AbstractRouterDistributor.java	0.00% <0.00%> (ø)
...pache/servicecomb/router/model/PolicyRuleItem.java	0.00% <0.00%> (ø)

... and 5 files with indirect coverage changes

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