make gray release rule case-insensitive

[nobodyiam]

What's the purpose of this PR

Make gray release rule case-insensitive

Which issue(s) this PR fixes:

Fixes #2092

Brief changelog

change grayReleaseRuleCache and reversedGrayReleaseRuleCache to be case insensitive

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• Read the Contributing Guide before making this pull request.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit tests to verify the code.
• Run mvn clean test to make sure this pull request doesn't break anything.

[codecov-io]

Codecov Report

Merging #2928 into master will increase coverage by 0.02%.
The diff coverage is 83.33%.

@@             Coverage Diff              @@
##             master    #2928      +/-   ##
============================================
+ Coverage     51.21%   51.24%   +0.02%     
- Complexity     2216     2218       +2     
============================================
  Files           431      431              
  Lines         13297    13300       +3     
  Branches       1366     1366              
============================================
+ Hits           6810     6815       +5     
+ Misses         6010     6009       -1     
+ Partials        477      476       -1

Impacted Files	Coverage Δ	Complexity Δ
...work/apollo/common/dto/GrayReleaseRuleItemDTO.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...lo/biz/grayReleaseRule/GrayReleaseRulesHolder.java	72.44% <100%> (+0.44%)	30 <0> (ø)	⬇️
...ollo/biz/grayReleaseRule/GrayReleaseRuleCache.java	87.5% <100%> (+0.54%)	11 <1> (+1)	⬆️
.../apollo/internals/RemoteConfigLongPollService.java	80.72% <0%> (+1.2%)	29% <0%> (+1%)	⬆️

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[coveralls]

Coverage increased (+0.02%) to 54.82% when pulling 82555eb on nobodyiam:fix-appid-case into 62cdc90 on ctripcorp:master.