fix 2.0.x bugs

[daizhenyu]

What type of PR is this?

Bug.

What this PR does / why we need it?

Integrate the bugs that have been resolved in the 2.1 branch to the 2.0.x branch

Which issue(s) this PR fixes？

Fixes #1589
Fixes #1591
Fixes #1602
Fixes #1610
Fixes #1613
Fixes #1616
Fixes #1654
Fixes #1666
Fixes #1674
Fixes #1685
Fixes #1687

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 51.87970% with 64 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ermant/registry/service/impl/GraceServiceImpl.java	78.57%	3 Missing and 6 partials ⚠️
.../io/sermant/core/config/utils/ConfigValueUtil.java	0.00%	4 Missing ⚠️
...ain/java/io/sermant/core/event/EventCollector.java	20.00%	4 Missing ⚠️
...ant/core/plugin/classloader/PluginClassLoader.java	0.00%	3 Missing ⚠️
...ion/okhttpv2/interceptors/OkHttp2xInterceptor.java	50.00%	1 Missing and 2 partials ⚠️
...c/main/java/io/sermant/core/AgentCoreEntrance.java	0.00%	2 Missing ⚠️
...ermant/core/event/collector/LogEventCollector.java	0.00%	2 Missing ⚠️
...src/main/java/io/sermant/core/utils/FileUtils.java	60.00%	2 Missing ⚠️
.../io/sermant/backend/dao/redis/RedisClientImpl.java	0.00%	2 Missing ⚠️
...ackend/dao/redis/RedisStandAloneOperationImpl.java	0.00%	2 Missing ⚠️
... and 16 more

Flag	Coverage Δ	Complexity Δ
unittests	43.17% <51.87%> (+0.27%)	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
...in/java/io/sermant/core/common/CommonConstant.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ain/java/io/sermant/core/common/LoggerFactory.java	20.00% <100.00%> (ø)	0.00 <0.00> (ø)
.../core/event/collector/FrameworkEventCollector.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...rvice/dynamicconfig/nacos/NacosBufferedClient.java	53.22% <100.00%> (+6.47%)	0.00 <0.00> (ø)
...ment/service/httpserver/HttpServerServiceImpl.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...va/io/sermant/backend/common/conf/CommonConst.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...java/io/sermant/backend/service/ConfigService.java	29.07% <ø> (+0.99%)	0.00 <0.00> (ø)
...mant/router/common/event/RouterEventCollector.java	25.64% <ø> (-5.32%)	0.00 <0.00> (ø)
...try/config/RegistryConfigSubscribeServiceImpl.java	17.39% <ø> (+1.39%)	0.00 <0.00> (ø)
...n/java/io/sermant/registry/utils/RefreshUtils.java	87.17% <100.00%> (ø)	0.00 <0.00> (ø)
... and 28 more

... and 27 files with indirect coverage changes