Optimize code and improve readability

[lilai23]

What type of PR is this?

Refactor

What this PR does / why we need it?

Some parts of the code have issues with logic consistency and readability.

Which issue(s) this PR fixes？

Fixes #1672

Does this PR introduce a user-facing change?

No

Checklist

• Make sure there is a GitHub_issue related with this PR before you start working on it.
• Make sure you have squashed your change to one single commit.
• GitHub Actions works fine in this PR.

[codecov]

Codecov Report

Attention: Patch coverage is 18.66667% with 61 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...mant/implement/service/xds/handler/XdsHandler.java	4.16%	23 Missing ⚠️
...ermant/core/plugin/config/PluginConfigManager.java	0.00%	20 Missing ⚠️
...o/sermant/backend/service/PageTemplateService.java	0.00%	15 Missing ⚠️
...sermant/mq/grayscale/config/MqGrayscaleConfig.java	0.00%	0 Missing and 1 partial ⚠️
...cketmq/service/RocketMqConsumerGroupAutoCheck.java	0.00%	1 Missing ⚠️
...o/sermant/router/common/metric/MetricsManager.java	87.50%	1 Missing ⚠️

Flag	Coverage Δ	Complexity Δ
unittests	43.95% <18.66%> (-0.02%)	181.00 <0.00> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ	Complexity Δ
...e/service/xds/entity/match/RegexMatchStrategy.java	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
...nt/implement/service/xds/utils/XdsCommonUtils.java	100.00% <ø> (ø)	0.00 <0.00> (ø)
...va/io/sermant/mq/grayscale/config/GrayTagItem.java	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
...e/rocketmq/utils/RocketMqGrayscaleConfigUtils.java	66.66% <100.00%> (ø)	0.00 <0.00> (ø)
.../rocketmq/utils/RocketMqSubscriptionDataUtils.java	68.00% <100.00%> (ø)	0.00 <0.00> (ø)
...outer/common/xds/lb/XdsRoundRobinLoadBalancer.java	66.66% <100.00%> (ø)	0.00 <0.00> (ø)
...sermant/mq/grayscale/config/MqGrayscaleConfig.java	78.94% <0.00%> (ø)	0.00 <0.00> (ø)
...cketmq/service/RocketMqConsumerGroupAutoCheck.java	17.04% <0.00%> (ø)	0.00 <0.00> (ø)
...o/sermant/router/common/metric/MetricsManager.java	39.53% <87.50%> (ø)	0.00 <0.00> (ø)
...o/sermant/backend/service/PageTemplateService.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
... and 2 more

... and 3 files with indirect coverage changes

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